MCQExams
0:0:1
CBSE
JEE
NTSE
NEET
Practice
Homework
×
CBSE Questions for Class 12 Medical Physics Wave Optics Quiz 2 - MCQExams.com
CBSE
Class 12 Medical Physics
Wave Optics
Quiz 2
A plane wave front falls on a convex lens. The emergent wave front is :
Report Question
0%
plane
0%
cylindrical
0%
spherical diverging
0%
spherical converging
Explanation
A convex lens is thicker at the middle. When a light ray is incident parallel
to principle axis it is refracted towards the focal point. Similarly when a plane wave front is incident on a convex lens the light is refracted towards a point on the focal plane.
As the light is getting focused at a point it is converging and the emerging wave front is a spherical converging.
Light waves spreading from two sources produce steady interference only if they have:
Report Question
0%
congruence
0%
coherence
0%
same intensity
0%
same amplitude
Explanation
Interference refers to the interaction of waves that are correlated of coherent with each other. S
ustained interference takes place between waves which are coherent.
1: Primary waves can travel in all directions in an ether
2: Secondary waves can travel only in backward in an ether
Report Question
0%
1 is true, 2 is false
0%
Both 1 and 2 are true
0%
1 is false, 2 is true
0%
Both 1 and 2 are false
Explanation
Primary wave can travel in all directions in ether.
Secondary waves can travel in forward direction in ether
The wavefronts gradually spread in all the directions. So at every point, we have a wave coming out. The primary wavefront is formed and again from the primary wavefront, a secondary waveform is formed and so on. The disturbance does not last for a long time.
Match list A and list B accurately :
List A List B
a) spherical wave front e) linear source
b) plane wave front f) point light source
c) cylindrical wave front g) at infinite distance
Report Question
0%
( a, f ); ( b, g); ( c, e)
0%
( a, f ); ( b, e); ( c, g)
0%
( a, g ); ( b, f); ( c, e)
0%
( a, e ); ( b, g); ( c, f)
Explanation
A point light source emits a spherical wave front because a point light source is not selective of any direction and emits equally in all directions. A linear source is made of many point sources. The spherical wave front coming out from these point sources interfere with each other and produce a cylindrical wave front.
when the source is at infinite distance then the wave front as a plane wave front because a plane wave front has infinite radius.
The sources which can give sustained interference are:
Report Question
0%
two independent laser sources
0%
two independent light bulbs
0%
two light sources of very large width
0%
two sources far away from one other
Explanation
Laser sources produce light waves which are coherent. As sustained interference takes place between waves, which are coherent, we can use two independent laser sources for the same.
In a Laser beam the photons emitted are :
Report Question
0%
incoherent
0%
coherent
0%
of same velocity
0%
of same wavelength
Explanation
LASER refers to light amplification based on the stimulated emission of Radiation. It emits light coherently. Thus the photons emitted in a laser beam are coherent.
Neutron diffraction pattern is used to determine :
Report Question
0%
density of solids
0%
atomic number of elements
0%
crystal structure of solid
0%
refractive index of liquid
Explanation
Neutron diffraction is used for the determination of the atomic structure of a material.
Sun light filtering through the tree leaves often makes circular patches on the ground because:
Report Question
0%
the sun is round
0%
the space through which light penetrates is round
0%
light is transverse in nature
0%
of diffraction effects
Explanation
Diffraction makes the circular patches on the ground which occured when a wave encountered the tree leaves.
The bending of light about corners of an obstacle is called :
Report Question
0%
Dispersion
0%
Refraction
0%
Deviation
0%
Diffraction
Explanation
$${\textbf{Explanation:}}$$
$$\bullet$$ The bending of a beam of light around the corners of the obstacles is called diffraction.
$$\bullet$$ The silver lining which we witness in the sky is caused due to diffraction of light. When the sunlight passes through or encounters the cloud, a silver lining is seen in the sky.
$${\textbf{Correct option: D}}$$
Two waves having the same wavelength and amplitude but having a constant phase difference with time are known as :
Report Question
0%
identical waves
0%
incoherent waves
0%
coherent waves
0%
collateral waves
Explanation
When the light waves are emitted from a single source and they have a constant phase difference between them then the waves are said to be coherent.
Option C is correct .
To observe diffraction, the size of an obstacle:
Report Question
0%
should be of the same order as wave length
0%
should be much larger than the wave length
0%
has no relation to wave length
0%
may be greater or smaller than the wave length
Explanation
$${\textbf{Explanation:}}$$
$$\bullet$$ The bending of a beam of light around the corners of the obstacles is called diffraction.
$$\bullet$$ It occurs only when the wavelength is comparable to the size of aperture. As the wavelength
increases, the diffraction effect will also increase.
$$\bullet$$ Thus for greater diffraction, it is important that the size of the obstacle is directly proportional to the wavelength of the source. Suppose $$a$$ is diffraction and $$\lambda$$ is the wavelength $$a \propto \lambda $$ Hence for diffraction, size of obstacle should be in the order of a wavelength due to wave nature of light.
$${\textbf{Correct option: A}}$$
A: Radio wave can diffract at the edges of buildings
B: X-rays can diffract at the interiors of a crystal
Report Question
0%
A is true, B is false
0%
Both A and B are true
0%
A is false, B is true
0%
Both A and B are false
Explanation
Diffraction overs when the size of obstacle is comperable to the wavelength of the incident waves . For radio wave , wavelength is of the order of $$10^{2}$$ ; while for $$x-rays$$ , wavelength has an order of $$\sim 10^{-6}$$ m.
One of the following statements is correct. Pick out the one.
Report Question
0%
Diffraction can not take place without interference
0%
Sustained interference will not take place without diffraction for non-coherent sources
0%
Interference and diffraction are the result of polarization
0%
The fringe width in Young's double slit experiment does not depends on the wave length.
Explanation
Yes, diffraction without interference can be possible.
Conditions for sustained interference pattern:
1. The two sources of light must be coherent with same frequency or wavelength and with same phase or constant phase difference.
2. The two sources should preferably have the same amplitude.
3. The two sources must be very close to each other.
4. The sources should emit light waves continuously.
Hence, sustained interference will not take place.
Interference and diffraction are not the results of polarization.
Finge width in Young's double slit experiment does depend on wavelength.
Polarisation of light was first successfully explained by:
Report Question
0%
Corpuscular theory
0%
Huygens' wave theory
0%
Electromagnetic wave theory
0%
Planck's theory
Explanation
Electromagnetic wave theory explains light as being composed of electric field vibrating in planes.
Polarisation of light refers to vibrating electric field in a particular plane.
Bartholinus discovered :
Report Question
0%
Interference by splitting the wave front
0%
Polarisation by reflection
0%
Polarisation by refraction
0%
Polarisation by double refraction
Explanation
In 1669, another Danish scientist, Erasmus Bartholinus discovered the polarization of light by double refraction in Iceland spar (calcite).
In Young's double slit experiment :
Report Question
0%
only interference occurs
0%
only diffraction occurs
0%
both interference and diffraction occurs
0%
polarisation occurs
Explanation
Diffraction always accompanies interference because it requires a single wave which interferes with itself.
Thus both interference and diffraction occur.
In an interference pattern produced by two identical slits, the intensity at the site of the central maximum is I. The intensity at the same spot when either of the two slits is closed is $$I_{\circ}$$. We must have:
Report Question
0%
$$I = I_{\circ}$$
0%
$$I = 2I_{\circ}$$
0%
$$ I = 4I_{\circ}$$
0%
$$ I$$ and $$I_{\circ}$$ are not related
Explanation
In case of constructive interference of waves due to 2 slits is, the intensity of central maxima is given by,
$$ E^2 = E_1^2 + E_2^2 + 2 E_1 E_2 $$
where E is the amplitude. For coherent sources, $$ E^2 = I $$
Hence, $$ I = I_0 + I_0 + 2I_o $$
Or $$I = 4$$ $$ I_0 $$
Light travels in a straight line because :
Report Question
0%
it is not absorbed by atmosphere
0%
its velocity is very high
0%
diffraction effect is negligible
0%
due to interference
Explanation
Diffraction is the effect which causes light to change path when it meets obstacles. But as diffraction effect is very small light travels in straight line .
Plane of polarisation is:
Report Question
0%
the plane in which vibrations of the electric vector takes place
0%
a plane perpendicular to the plane in which vibrations of the electric vector takes place
0%
perpendicular to the plane of vibration
0%
horizontal plane
Explanation
$$ \bf{Plane\ of\ Vibrations} $$ is the plane in which the vibrations of electric vector of plane polarized light are present.
$$ \bf{Plane\ of\ Polarization} $$ is the plane perpendicular to the plane of vibration and in this plane, the vibrations of the electric vector are absent.
Hence, the correct answers are OPTIONS B and C.
A: Coloured spectrum is seen when we look through a cloth
R: Diffraction of light takes place when light is travelling through the pores of cloth
Report Question
0%
A is false but R is true
0%
Both A and R are true, and R is not correct explanation of A
0%
Both A and R are true, and R is correct explanation of A
0%
A is true but R is false
Explanation
Coloured spectrum is obtained when interference of ight takes place.
In a cloth only diffraction of light takes place when light is travelling through the pores of cloth.
Thus only R is correct.
Both light and sound waves produce diffraction. It is more difficult to observe the diffraction with light waves because:
Report Question
0%
light wave do not require medium
0%
wavelength of light waves is far smaller
0%
light waves are transverse
0%
speed of light is far greater
Explanation
Diffraction is bending of a wave around objects. It is most noticeable when the obstruction or gap is about the same size as the wavelength of the incident wave.
Wavelength of light is in the order of hundreds of nanometre $$(\sim 10^{-9}m$$ while the wavelength of sound lies in a range of $$10^{-1}m$$ to $$10^{-2}m)$$.
In our macroscopic world, objects have size comparable to the wavelength of sound, therefore diffraction with light is difficult to observe.
ASSERTION (A):Hyugens' theory failed to explain polarization
REASON (R): According to Hyugens' theory light is longitudinal wave
Report Question
0%
A is correct, R is correct and it is the correct explanation
0%
A is correct, R is correct but it is not a correct explanation
0%
A is correct, R is wrong
0%
A is wrong , R is correct
Explanation
Huygen's theory failed to explain polarisation because according to the Huygen's theory light is a longitudinal waves and longitudinal wave does not shows polarisation.
To increase both the resolving power and magnifying power of a telescope
Report Question
0%
Both the focal length and aperture of the objective has to be increased.
0%
The focal length of the objective has to be increased.
0%
The aperture of the objective has to be increased.
0%
The wavelength of light has to be decreased.
Explanation
Resolving power, $$R=\dfrac{a}{1.22 \lambda}$$
where, $$a$$ is diameter of objective $$\lambda$$ is wavelength of light
magnifying power $$m=\dfrac{-f_{0}}{f_{e}}\left ( 1+\dfrac{f_{e}}{D} \right )$$
so, decreasing the wavelength of light increases the resolving power and magnifying power of telescope.
An electron microscope is superior to an optical microscope in terms of:
Report Question
0%
having better resolving power
0%
being easy to handle
0%
low cost
0%
quickness of observation
Explanation
The biggest advantage of an electron microscope over optical microscope is that they have a higher resolution and are therefore capable of a higher magnification ( up to $$2 \ million$$ times ).
However, optical microscopes show a useful magnification up to $$1000-2000 $$ times.
This is a limit imposed by the wavelength of light. Electron
microscopes, therefore,
allow for the visualization of structures that would normally be not visible by optical microscopy.
The resolving power of human eye is :
Report Question
0%
$$\approx 1'$$
0%
$$\approx 1^{0}$$
0%
$$\approx 10"$$
0%
$$\approx 5"$$
Explanation
$${\textbf{Explanation:}}$$
$$\bullet$$ As we know the visibility of the human eye is limited up to a distance.
$$\bullet$$ It is known to us that the normal pupil size of any human being is 4 mm. This measurement sets a minimum resolution approximately 1' to 2′.
$$\bullet$$ When we want to pull small objects closer to our eyes, we aim to see them properly. But it is often seen that after crossing a certain distance the particles become unclear no matter how much closer it is to our eyes.
$$\bullet$$ This signifies that there is a minimum distance of comfortable viewing. This distance is roughly calculated as 25 cm.
$${\textbf{Correct option: A}}$$
In YDSE, the slit widths are in the ratio of $$1: 9$$.The ratio of intensity of the maxima to that of the minima is :
Report Question
0%
$$81 :1$$
0%
$$9 : 1$$
0%
$$4 : 1$$
0%
$$3 : 1$$
Explanation
Intensity is proportional to the area of the slit.
As slit widths are in the ratio of $$1 : 9$$
The areas are also in the ratio $$1 : 9$$
Thus Intensities are in the ratio $$1 : 9$$
amplitudes are square root of Intensities
Thus amplitudes are in ratio $$1 : 3$$
Let amplitudes be $$x$$ and $$3x$$
At maxima the amplitudes get added up $$x+3x$$
$$=4x$$
At minima they become $$x-3x=-2x$$
Intensity of maxima to minima is $$\dfrac{16x^{2}}{4x^{2}}=\dfrac{4}{1}$$
Fill in the blanks:
According to Newton, different colors of light are due to the difference in _______ of the corpuscles.
Report Question
0%
mass
0%
nature
0%
shape
0%
size
Explanation
Corpuscles are single, infinitesimally small, particles which have shape, size, color, and other physical properties.
The angular resolution of a telescope of 10 cm diameter at a wavelength of 5000Å is of the order of:
Report Question
0%
10$$^{6}$$ rad
0%
$$10^{-2}$$ rad
0%
$$10^{-4}$$ rad
0%
$$10^{-5}$$ rad
Explanation
$$R= \dfrac{1}{\Delta \theta }= \dfrac{a}{1.22\lambda }$$
$$\dfrac{1}{\Delta \theta }= \dfrac{0.10}{1.22\times 5000\times 10^{-10}}$$
$$\Delta \theta = 6.1\times 10^{-6}\ rad$$
The radius of a wavefront as the waves propagate
Report Question
0%
decreases
0%
increases
0%
becomes zero
0%
sometimes decreases and sometimes increases.
Explanation
As the waves propagates, it goes on creating secondary sources of light, resulting in increase in its radius.
Interference takes place whenever two or more wave motions combine in space. (True or False)
Report Question
0%
True
0%
False
Explanation
Interference
is a phenomenon in which two waves superimpose
to form a resultant wave of greater or lower amplitude
. Interference usually refers to the interaction of waves that are correlated or coherent
with each other, either because they come from the same source or because they have the same or nearly the same frequency.
Two coherent waves of light will not produce constructive interference if the phase difference between them is
Report Question
0%
$$0^0$$
0%
$$360^0$$
0%
$$720^0$$
0%
$$90^0$$
Explanation
Constructive interference for coherent waves takes place when phase difference = $$2n\pi$$ where n is a integer
So the only case in the options when constructive interference will not take place is $$90^\circ$$
Answer. D
Newton postulated his corpuscular theory of light on the basis of:
Report Question
0%
Newton's rings.
0%
rectilinear propagation of light.
0%
colour through thin films.
0%
Dispersion of white light into colours.
Explanation
According to
Isaac Newton the geometric nature of reflection and refraction of light could only be explained if light was made of particles, referred to as corpuscles that travel in straight line.
How can resolving power of the instrument be increased?
Report Question
0%
use UV light
0%
immerse in oil
0%
use IR light
0%
use one more lens.
Explanation
Resolving power for the instrument is found to be
$$\dfrac{\mu\sin\theta}{0.61\lambda}$$ ,
UV light has short wavelength, hence higher resolving power.
Oil is optically denser than air, that is, its $$\mu$$ is greater than that of air. Thus immersing in oil would increase the resolving power.
The interplaner distance in a crystal is 2.8 x $$10^{-8}$$ m. The value of maximum wavelength which can be diffracted :
Report Question
0%
2.8 x $$10^{-8}$$ m
0%
5.6 x $$10^{-8}$$ m
0%
1.4 x $$10^{-8}$$ m
0%
7.6 x $$10^{8}$$ m
The time of coherence is of the order of
Report Question
0%
$$10^{-4}s$$
0%
$$10^{-8}s$$
0%
$$10^{-6}s$$
0%
$$10^{-2}s$$
Explanation
In a light source, a light wave(photon) is produced when an excited atom goes to the ground state and emits light.
The duration of this transition is $$10^{-8}s$$. Thus the emitted wave remains sinusoidal for this much time. This time is known as coherence time($$\tau_c$$).
The device which produces highly coherent sources is
Report Question
0%
Fresnel biprism
0%
Young's double sit
0%
Laser
0%
Lloyd's mirror
Explanation
The atoms in the laser medium are pumped up energetically by an external power source, producing a population inversion of atomic energies. The pumped-up atoms can return to lower energy levels by emitting light at only certain frequencies, depending on the particular medium, which can be a solid (e.g. laser diode), a liquid (e.g. dye laser) or a gas (e.g. helium-neon laser).
We get temporal coherence because the excited atoms emit only at that preferred frequency.
The air film in a Newton's ring apparatus is replaced by an oil film. The radii of the rings
Report Question
0%
remains the same
0%
increases
0%
decreases
0%
none of the above
Explanation
Radius of nth order Newton's ring is proportional to $$\sqrt{\lambda}$$ which decreases in oil since $$\lambda=\dfrac{\lambda_{vacuum}}{\mu}$$. Thus the radius of newton's ring decreases in oil film.
Huygens principle of secondary waves
Report Question
0%
allow us to find the focal length of a thick convex lens.
0%
give us the magnifying power of the microscope.
0%
is a geometrical method to find, the position of a wave front.
0%
is used to determine the velocity of light.
Explanation
Huygens's Principle states that every point on a wavefront is a source of secondary wavelets, which spread forward at the same speed.
Thus is enables to find the position of wavefront.
Coherence is a measure of
Report Question
0%
capability of producing interference by wave
0%
waves being diffracted
0%
waves being reflected
0%
waves being refracted
Explanation
Interference is a phenomenon in which two waves
superpose to form a resultant wave
of greater or lower amplitude.
If the sources are coherent, the interference pattern obtained is more ordered, with definite spacing between fringes.
Thus coherence is a measure of capability of producing interference of wave.
The time of coherence is of the order of
Report Question
0%
$$10^{-4}s$$
0%
$$10^{-8}s$$
0%
$$10^{-6}s$$
0%
$$10^{-2}s$$
Explanation
In a light source(photon) is produced when an excited atom goes to the ground state and emits light.
The duration of the transition is about $$10^{-8}s$$. Thus the emitted light remains sinusoidal for this much time. This is called the coherence time($$\tau_c$$).
Which of the following undergo maximum diffraction?
Report Question
0%
$$\alpha -rays$$
0%
$$\gamma -rays$$
0%
radio waves
0%
light waves
Explanation
Wavelength of a wave is a factor which decides maximum size of obstacle which can cause diffraction. Radio waves have largest wavelength hence will cause maximum diffraction.
Answer. C) Radio waves.
Which of the following, cannot produce two coherent sources?
Report Question
0%
Lloyd's mirror
0%
Fresnel biprism
0%
Young's double sit
0%
Prism
Explanation
Two coherent sources are produced in Lloyd's mirror by reflection of light from a plane mirror, hence the original source and its image acting as coherent sources.
In fresnel biprism, light from a point source gets refracted by a biprism to produce two coherent sources.
In Young's double slit, two coherent sources are produced by passing of light from a single source through two slits.
The correct relation between the size of the obstacle and wavelength of light in order to observe the diffraction effect is
Report Question
0%
$$ a_{\displaystyle^/\lambda}=0$$
0%
$$a_{\displaystyle^/\lambda}=0^.$$
0%
$$a_{\displaystyle^/\lambda}=\infty$$
0%
$$a_{\displaystyle^/\lambda}=150$$
Explanation
The wavelength of light used must be very small compared to the slit size.
If the slit size (or distance between two slits) is much smaller than the wavelength, it effectively acts like a single point and the waves propagate radially in all directions. If the slit size is much larger than the wavelength, it's like "no slit" – free propagation – and rays may propagate through the slit (almost) without disturbance.
Huygens's concept of secondary wave
Report Question
0%
allows us to find the focal length of a thick lens
0%
is a geometrical method to a find a wavefront
0%
is used to determine the velocity of light
0%
is used to explain polarisation
Explanation
Huygens principle states that "Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light. The new wave-front is the tangential surface to all of these secondary wavelets."
Thus it is geometrical method to find the wavefront.
Which of the following cannot be polarised ?
Report Question
0%
Radio waves
0%
$$\beta$$ rays
0%
Infrared rays
0%
$$\gamma$$ rays
Explanation
$$ \beta $$ are stream of particles comprising of electrons moving with very high velocity, hence it cannot be polarized, while others can as they are electromagnetic waves.
Huygen's concept of wavelets is useful in
Report Question
0%
explaining polarisation
0%
determining focal length of lenses
0%
determining chromatic aberration
0%
geometrical reconstruction of a wavefront
Explanation
Huygens considered that light was propagated in longitudinal waves.
Huygen's concept explained the direction of propagation of light waves by geometrical reconstruction of wavefront.
At the centre (t = 0) of Newton's ring arrangement, we observe a
Report Question
0%
dark spot
0%
bright spot
0%
coloured spot
0%
None of these
Explanation
In Newton ring experiment, the band forms are circular in nature and at the centre there is presence of dark spot due to destructive interference.
Polarisation of light establishes
Report Question
0%
corpuscular theory of light
0%
quantum nature of light
0%
transverse nature of light
0%
all of the above
Explanation
Polarisation of light establishes that light are transverse in nature, otherwise it was believed that they are longitudinal waves, like the sound waves.
The spectrum in which the colors are separated using a narrow source of light is called:
Report Question
0%
pure spectrum
0%
rainbow
0%
impure spectrum
0%
none of these
Explanation
A spectrum of light in which no two wavelengths (colours) overlap with each other is called a pure spectrum. A pure spectrum is formed when white light is passed through a narrow slit and the incident rays are parallel to each other.
Choose the correct option about light.
Report Question
0%
Light requires a material medium to travel from one place to another
0%
Light does not require a material medium to propagate
0%
Light has mass but it is negligible
0%
Light waves are longitudinal wave
Explanation
Light does not need medium to travel. Its an electromagnetic wave. All
electromagnetic
waves travel independent of medium.
0:0:1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
0
Answered
0
Not Answered
0
Not Visited
Correct : 0
Incorrect : 0
Report Question
×
What's an issue?
Question is wrong
Answer is wrong
Other Reason
Want to elaborate a bit more? (optional)
Practice Class 12 Medical Physics Quiz Questions and Answers
<
>
Support mcqexams.com by disabling your adblocker.
×
Please disable the adBlock and continue.
Thank you.
Reload page
