JEE Questions for Physics Ray Optics Quiz 18 - MCQExams.com

If the focal length of the objective lens is increased then
  • Magnifying power of microscope will increase but that of telescope will decrease
  • Magnifying power of microscope and telescope both will increase
  • Magnifying power of microscope and telescope both will decrease
  • Magnifying power of microscope will decrease but that of telescope will increase
At Kavalur in India, the astronomers using a telescope whose objective had a diameter of one metre started using a telescope of diameter 2.54 m. This resulted in
  • The increase in the resolving power by 2.54 times for the same λ
  • The increase in the limiting angle by 2.54 times for the same λ
  • Decrease in resolving power
  • No effect on the limiting angle
The focal lengths of the objective and the eye-piece of a compound microscope are 2.0 cm and 3.0 cm respectively. The distance between the objective and the eye-piece is 15.0 cm. The final image formed by theeye-piece is at infinity. The two lenses are thin. The distances in cm of the object and the image produced by the objective measured from the objective lens are respectively
  • 2.4 and 12.0
  • 2.4 and 15.0
  • 2.3 and 12.0
  • 2.3 and 3.0
Resolving power of a microscope depends upon
  • The focal length and aperture of the eye lens
  • The focal lengths of the objective and the eye lens
  • The apertures of the objective and the eye lens
  • The wavelength of light illuminating the object
The objective lens of a compound microscope produces magnification of 10. In order to get an overall magnification of 100 when image is formed at 25 cm from the eye, the focal length of the eye lens should be
  • 4 cm
  • 10 cm

  • Physics-Ray Optics-86284.png
  • 9 cm
A person using a lens as a simple microscope sees an
  • Inverted virtual image
  • Inverted real magnified image
  • Upright virtual image
  • Upright real magnified image
Least distance of distinct vision is 25 cm. Magnifying power of simple microscope of focal length 5 cm is
  • 1/5
  • 5
  • 1/6
  • 6
In a compound microscope cross-wires are fixed at thepoint
  • Where the image is formed by the objective
  • Where the image is formed by the eye-piece
  • Where the focal point of the objective lies
  • Where the focal point of the eye-piece lies
If the red light is replaced by blue light illuminating the object in a microscope the resolving power of themicroscope
  • Decreases
  • Increases
  • Gets halved
  • Remains unchanged
Two points separated by a distance of 0.1 mm can just be resolved in a microscope when a light of wavelength 6000 Å is used. If the light of wavelength 4800 Å isused this limit of resolution becomes
  • 0.08 mm
  • 0.10 mm
  • 0.12 mm
  • 0.06 mm
The angular magnification of a simple microscope can be increased by increasing
  • Focal length of lens
  • Size of object
  • Aperture of lens
  • Power of lens
Wavelength of light used in an opticalinstrument are λ1. = 4000 Å and λ2 = 5000 Å, then ratio of their respective resolving power (corresponding to λ1 and λ2) is
  • 16 : 25
  • 9 : 1
  • 4 : 5
  • 5 : 4
The separation between two microscopic particles is measured PA and PB by two different lights of wavelength 2000 Å and 3000 Å respectively, then
  • PA>PB
  • PAB
  • PA<3/2PB
  • PA = PB
Which of the following is not correct regarding the radio telescope?
  • It cannot work at night
  • It can detect a very faint radio signal
  • It can be operated even in cloudy weather
  • It is much cheaper than optical telescope
A simple telescope, consisting of an objective of focal length 60 cm and a single eye lens of focal length 5 cm is focused on a distant object is such a way that parallel rays come out from the eye lens. If the object subtends an angle 2° at the objective, the angular widthof the image
  • 10°
  • 24°
  • 50°
  • 1/6°
A photograph of the moon was taken with telescope. Later on, it was found that a housefly was sitting on the objective lens of the telescope. In photograph
  • The image of housefly will be reduced
  • There is a reduction in the intensity of the image
  • There is an increase in the intensity of the image
  • The image of the housefly will be enlarged
To increase the magnifying power of telescope (f0 = focal length of the objective and fe = focal length of the eye lens)
  • f0 should be large and fe should be small
  • f0 should be small and fe should be large
  • f0 and fe both should be large
  • f0 and fe both should be small
Relative difference of focal lengths of objective and eye lens in the microscope and telescope is given as
  • It is equal in both
  • It is more in telescope
  • It is more in microscope
  • It may be more in any one
A simple magnifying lens is used in such a way that an image is formed at 25 cm away from the eye. In order to have 10 times magnification, the focal length of the lens should be
  • 5 cm
  • 2 cm
  • 25 mm
  • 0.1mm
A telescope of diameter 2m uses light of wavelength 5000 Å for viewing stars. The minimum angular separation between two stars whose image is just resolved by this telescope is
  • 4 × 10–4 rad
  • 0.25 × 10–6 rad
  • 0.31 × 10–6 rad
  • 5.0 × 10–3 rad
In Gallilean telescope, if the powers of an objective and eye lens are respectively +1.25 D and –20 D, then for relaxed vision, the length and magnification will be
  • 21.25 cm and 16
  • 75 cm and 20
  • 75 cm and 16
  • 8.5 cm and 21.25
The aperture of a telescope is made large, because
  • To increase the intensity of image
  • To decrease the intensity of image
  • To have greater magnification
  • To have lesser resolution
A Galileo telescope has an objective of focal length 100cm and magnifying power 50. The distance between the two lenses in normal adjustment will be
  • 96 cm
  • 98 cm
  • 102 cm
  • 104 cm
To increase both the resolving power and magnifyingpower of a telescope
  • Both the focal length and aperture of the objective has to be increased
  • The focal length of the objective has to be increased
  • The aperture of the objective has to be increased
  • The wavelength of light has to be decreased
A telescope has an objective of focal length 50 cm and an eye piece of focal length 5 cm. The least distance of distinct vision is 25 cm. The telescope is focused for distinct vision on a scale 200 cm away. The separation between the objective and the eye-piece is
  • 75 cm
  • 60 cm
  • 71 cm
  • 74 cm
A opera glass (Gallilean telescope) measure 9 cm from the objective to the eyepiece. The focal length of the objective is 15 cm. Its magnifying power is
  • 2.5
  • 2/5
  • 5/3
  • 0.4
The aperture of the objective lens of a telescope ismade large so as to
  • Increase the magnifying power of the telescope
  • Increase the resolving power of the telescope
  • Make image aberration less
  • Focus on distant objects
On which of the following does the magnifying power of a telescope depends
  • The focal length of the objective only
  • The diameter of aperture of the objective only
  • The focal length of the objective and that of the eye piece
  • The diameter of aperture of the objective and that of the eye piece
The diameter of the objective lens of a telescope is 5.0 m and wavelength of light is 6000 Å. The limit of resolution of this telescope will be
  • 0.03 sec
  • 3.03 sec
  • 0.06 sec
  • 0.15 sec
A terrestrial telescope is made by introducing an erecting lens of focal length f between the objective and eye piece lenses of an astronomical telescope. This causes the length of the telescope tube to increase by an amount equal to
  • f
  • 2f
  • 3 f
  • 4f
The length of an astronomical telescope for normal vision (relaxed eye) f0 = focal length of objective lens and fe = focal length of eye lens) is

  • Physics-Ray Optics-86305.png
  • 2)
    Physics-Ray Optics-86306.png

  • Physics-Ray Optics-86307.png

  • Physics-Ray Optics-86308.png
A Gallilean telescope has objective and eye-piece of focal lengths 200 cm and 2 cm respectively. The magnifying power of the telescope for normal vision is
  • 90
  • 100
  • 108
  • 198
The resolving power of a telescope depends on
  • Focal length of eye lens
  • Focal length of objective lens
  • Length of the telescope
  • Diameter of the objective lens
When diameter of the aperture of the objective of an astronomical telescope is increased, its
  • Magnifying power is increased and resolving power is decreased
  • Magnifying power and resolving power both are increased
  • Magnifying power remains the same but resolving power is increased
  • Magnifying power and resolving power both are decreased
The minimum magnifying power of a telescope is M, If the focal length of its eye lens is halved, the magnifying power, will become
  • M/2
  • 2 M
  • 3 M
  • 4 M
The astronomical telescope consists of objective and eyepiece. The focal length of the objective is
  • Equal to that of the eye-piece
  • Greater than that of the eye-piece
  • Shorter than that of the eye-piece
  • Five times shorter than that of the eye-piece
Four convergent lenses have focal lengths 100 cm, 10 cm, 4 cm and 0.3 cm. For a telescope with maximum possible magnification, we choose the lenses of focal length
  • 100 cm, 0.3 cm
  • 10 cm, 0.3 cm
  • 10 cm, 4 cm
  • 100 cm, 4 cm
The sun\'s diameter is 1.4 × 109m and its distance fromthe earth is 1011 nm. The diameter of its image, formed by a convex lens of focal length 2 m will be
  • 0.7 cm
  • 1.4 cm
  • 2.8 cm
  • Zero (i.e., point image)
The focal lengths of the objective and of the eye-piece of a compound microscope are f0 and fe respectively. If L is the tube length and D, the least distance of distinct vision, then its angular magnification, when the image is formed at infinity, is

  • Physics-Ray Optics-86315.png
  • 2)
    Physics-Ray Optics-86316.png

  • Physics-Ray Optics-86317.png

  • Physics-Ray Optics-86318.png
The length of a telescope is 36 cm. The focal lengths of its lenses can be
  • 30 cm, 6 cm
  • – 30 cm, – 6 cm
  • 30 cm, – 6 cm
  • – 30 cm, 6 cm
An astronomical telescope of ten-fold angular magnification has a length of 44 cm. The focal length of the objective is
  • 4 cm
  • 40 cm
  • 44 cm
  • 440 cm
If both the object and image are at infinite distance from a refracting telescope its magnifying power will be equal to
  • The sum of the focal lengths of the objective and the eyepiece
  • The difference of the focal lengths of the two lenses
  • The ratio of the focal length of the objective and eyepiece
  • The ratio of the focal length of the eyepiece and objective
The number of lenses in a terrestrial telescope is
  • Two
  • Three
  • Four
  • Six
The focal lengths of the lenses of an astronomical telescope are 50 cm and 5 cm. The length of the telescope when the image is formed at the leastdistance of distinct vision is
  • 45 cm
  • 55 cm

  • Physics-Ray Optics-86323.png

  • Physics-Ray Optics-86324.png
If luminous efficiency of a lamp is 2 lumen/watt and its luminous intensity is 42 candela, then power of the lamp is
  • 62 W
  • 76 W
  • 138 W
  • 264 W
An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2m away from the bulb is 5 × 10–4 phot (lumen/cm2). Theline joining the bulb to the point makes an angle of 60° with the normal to the surface. The intensity of the bulb in candela is
  • 40√3
  • 40
  • 20
  • 40 × 10–4
In a movie hall, the distance between the projector and the screen is increased by 1% illumination on the screen is
  • Increased by 1%
  • Decreased by 1%
  • Increased by 2%
  • Decreased by 2%
Correct exposure for a photographic print is 10 seconds at a distance of one metre from a point source of 20 candela. For an equal fogging of the print placed at a distance of 2 m from a 16 candela source, the necessary time for exposure is
  • 100 s
  • 25 s
  • 50 s
  • 75 s
A bulb of 100 watt is hanging at a height of one meter above the centre of a circular table of diameter 4 m. If the intensity at a point on its rim is I0, then the intensity at the centre of the table will be

  • Physics-Ray Optics-86330.png
  • 2)
    Physics-Ray Optics-86331.png

  • Physics-Ray Optics-86332.png

  • Physics-Ray Optics-86333.png
A movie projector forms an image 3.5m long of an object 35 mm. supposing there is negligible absorption of light by aperture then illuminance on slide and screen will be in the ratio of
  • 100 : 1
  • 104 : 1
  • 1 : 100
  • 1 : 104
0:0:1


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