When the intensity of a light source is increased, (a) the number of photons emitted by the source in unit time increases

(a) point source EXPLANATION:  Only for a point source the intensity can be written as I = E/4πr², where E is the strength of the source. Hence  E ∝ 1/r².

The correct answer is (c) 2 f EXPLANATION:  The intensity of the light on the other side is maximum where the image of the point source is formed.  Here u = -2f, f...

Overall luminous efficiency =Total luminous flux / Power input =35x685/100 = 239.75 lumen/W

The correct answer is (c) 2%

The correct answer is (c) 1/r

The correct answer is (1) When unpolarised light of intensity Io is incident on a polarizing sheet, only Io/2 is transmitted.

(c) Red bulb and a blue bulb of equal power in a given time nr > nb.

(a) the intensity of the source is increased

n1 = 2, n2 = 3 Energy possessed by Hα light = 13.6 (1/n12 – 1/n22) = 13.6 x (1/4 – 1/9) = 1.89 eV. For Hα light to be able to emit photoelectrons from a metal...

(a) Photons emitted while excited electrons drops down