A `0.6 xx 10^(-3) W` laser is aimed at the Moon. The wavelength of emitted light is 600 nm and the laser beam spreads out of the source at a divergence angle of `theta = 0.5 xx 10^(-3) rad`. The Earth-Moon distance is nearly `4 xx 108 m`. Calculate the maximum number of photons arriving per second per square meter on the Moon? Neglect any absorption by the atmosphere.
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A beam of ultraviolet light of all wavelength passes through hydrogen gas at room temperature, in the x-direction. Assume that all photons emitted due
Correct Answer - A::C::D Room temperature `rArr n = 1` Upon absorption excitations takes place to many higher states which upon de-excitation emit all U.V., infrared and visible light.
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A mirror and a source of light are situated at the origin `O` and at a point on `O X ,` respectively. A ray of light from the source strikes the mirro
Let the source of light be situated at `A(a, 0, 0)`, where `ane0`. Let `OA` be the incident ray and `OB` the reflected ray. `ON` is the normal to the...
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If a light with frequency `4xx10^(16) Hz` emitted photoelectrons with double the maximum kinetic as are emitted by the light of frequency `2.5xx10^(16
Correct Answer - `1xx10^(16) Hz` For frequency `2.5xx10^(16) Hz, h v=hv_(o)+KE_(max)` `:. h(2.5xx10^(16))=hv_(o)+KE_(max) ...(i)` For frequency `4xx10^(16)` Hz, `h(4xx10^(16))=hv_(o)+2KE_(max) ...(2)` Multiply `eq^(n)` (1) by `2` and substract `eq^(n)` (2) from it....
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A laser beam of wavelength `lambda_(1) = 5 xx 10^(– 7) m` strikes normally a blackened plate and produces a force of `10^(– 5) N`. Mass of the plate i
Correct Answer - `750 Ks^(-1)`
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A parallel beam of monochromatic light of frequency v is incident on a surface. Intensity of the beam is I and area of the surface is A. Find the forc
Correct Answer - (i) `(IA)/(c)` , (ii) `(2IA)/(c)` (iii) `(Iacostheta)/(c)` , (iv) `(2IAcos^(2)theta)/(c)`
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Find the number of photons emitted per second by a 25 W source of monochromatic light of wavelength `6600 Å`. What is the photoelectric current assumi
Correct Answer - `8.33 xx 10^(19), 0.4 A`
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Given that a photon of light of wavelength 10,000Å has an energy equal to 1.23eV. When light of wavelength 5000Å and intensity `I_(0)` falls on a phot
Correct Answer - (i) 1.1 eV (ii) `1.6 xx 10^(-6) A` ; unchanged
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A laser beam has a wavelength of `6xx10^(-7)`m and aperture of `6xx10^(-2)`m. The beam is sent towards the moon which is at a distance of `4xx10^(8)`m
Correct Answer - (i)`1.22xx10^(-5)rad(ii) 2.381xx10^(7)`m
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A laser beam has a power of 100 mW. It has an aperture of `5xx10^(-3)`m and emits a wavelength 6943 Å. The beam is focused with a lens of focal length
Correct Answer - `2.87xx10^(-10)m^(2),3.48xx10^(8)Wm^(-2)`
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A beam of light travelling in water falls on a glass plate immersed in water. When the incident angle is `51^(@)`, the reflected beam of light is foun
Correct Answer - 1.647
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