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JEE PHYSICS MCQ: DUAL NATURE OF RADIATION AND MATTER

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The cathode of a photoelectric cell is changed such that the work function changes from

{W_1}

to

{W_2}\left( {{W_2} > {W_1}} \right).

If the current before and after change are

{I_1}

and

{I_2},

all other conditions remaining unchanged, then (assuming

hv > {W_2}

)

View answer and explanation

Correct option: A

{I_1} = {I_2}

Option A (

{I_1} = {I_2}

) is correct because the photoelectric current depends on the intensity and frequency of the incident light and the number of photoelectrons emitted, but as long as the photon energy is greater than the work function, changing the work function does not affect the current.

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The electrons are emitted in the photoelectric effect from a metal surface What is the de Broglie wavelength of a bullet of mass 0.04 kg travelling at the speed of 1 km/s? Photoelectrons are emitted from a metal surface when UV light of wavelength

\lambda=300 \mathrm{~nm}

is incident on it. The minimum negative potential required to stop the emission of electrons is

0.54 \mathrm{~V}

. Calculate:
(i) the energy of the incident photons
(ii) the maximum kinetic energy of the photoelectrons emitted. An electron is accelerated by a potential difference of V volt to acquire kinetic energy equal to maximum kinetic energy of ejected photoelectron from a metal of work function 3.2 eV, using a light of wavelength

2000\,\mathop \mathrm{A}\limits^ \circ \,

Value of V is Two monochromatic beams

A

B

of equal intensity

I

, hit a screen. The number of photons hitting the screen by beam

A

is twice that by beam

B

. Then, what can inference you about their frequencies? A 5 W source emits monochromatic light of wavelength

5000\mathop A\limits^ \circ

. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0m, the number of photoelectrons liberated will be reduced by a factor of