Explanation
For a prism, as the angle of incidence increases, the angle of deviation first decreases, goes to a minimum value and then increases.
Due to blocking only intensity is going to decrease. Each part of reflection mean by put it.
Convex mirror and concave lens form virtual image for all positions of objects.
Only valid for paraxial rays.
Te stars twinkle while the planets do not. It is due to variation in density of atmospheric layer. As the stars are very far and giving light continuously to us. So. the light coming from stars is found to change their intensity continuously. Hence, they are seen twinkling. Also stars are much bigger in size than planets but it has nothing to deal with twinkling phenomenon.
Owls can move freely during night, because they have large number of cones on their retina which help them to see in night.
Shining of air bubble in water is on account of total internal reflection.
After the removal of stimulus the image formed on retina is sustained up to 1/6 second.
For total internal reflection the angle of incidence should be greater than the critical angle, As critical angle is 35°. Therefore, total internal reflection is not possible. So, assertion is not true but reason is true.
The red glass absorbs the radiations emitted by green flowers; so flower appears black.
The efficiency of fluorescent tube is about 50 lumen/watt, whereas efficiency of electric bulb is about 12 lumen/watt. Thus for same amount of electric energy consumed, the tube gives nearly 4 times more light than the filament bulb.
In search lights, we need an intense parallel beam of light. If a source is placed at the focus of a concave spherical mirror, only paraxial rays are rendered parallel. Due to large aperture of mirror, marginal rays give a divergent beam.
But in case of parabolic mirror, when source is at the focus, beam of Light produced over the entire cross-section of the mirror is a parallel beam.
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