Science (English Medium) Class 12 - CBSE Important Questions for Physics

A beam of monochromatic radiation is incident on a photosensitive surface. Answer the following question giving reason :

Do the emitted photoelectrons have the same kinetic energy?

A beam of monochromatic radiation is incident on a photosensitive surface. Answer the following question giving reason :

Does the kinetic energy of the emitted electrons depend on the intensity of incident radiation?

A beam of monochromatic radiation is incident on a photosensitive surface. Answer the following question giving reason :

On what factors does the number of emitted photoelectrons depend?

Plot a graph showing the variation of photoelectric current with collector plate potential at a given frequency but for two different intensities I₁ and I₂, where I₂ > I₁.

In photoelectric effect, why should the photoelectric current increase as the intensity of monochromatic radiation incident on a photosensitive surface is increased? Explain.

Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies, v₁ > v₂, of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.

Use Einstein’s photoelectric equation to show how from this graph, 
(i) Threshold frequency, and (ii) Planck’s constant can be determined.

Work function of aluminium is 4.2 eV. If two photons each of energy 2.5 eV are incident on its surface, will  the emission of electrons take place? Justify your answer. 

Define the term "Threshold frequency", in the context of photoelectric emission.  

Define the term: threshold frequency

Answer the following question.
Plot a graph of photocurrent versus anode potential for radiation of frequency ν and intensities I₁ and I₂ (I₁ < I₂).

On the basis of the graphs shown in the figure, answer the following questions :

(a) Which physical parameter is kept constant for the three curves?

(b) Which is the highest frequency among v₁, v_2, and v₃?

Use Einstein's photoelectric equation to show how from this graph,
(i) Threshold frequency, and
(ii) Planck's constant can be determined.

The work function of aluminum is 4⋅2 eV. If two photons each of energy 2⋅5 eV are incident on its surface, will the emission of electrons take place? Justify your answer.

Define the terms "stopping potential' and 'threshold frequency' in relation to the photoelectric effect. How does one determine these physical quantities using Einstein's equation?

Choose the correct answer from given options
Photons of frequency v are incident on the surface of two metals A and B of threshold frequency 3/4 v and 2/3 v, respectively. The ratio of maximum kinetic energy of electrons emitted from A to that from B is

In the case of a photo electric effect experiment, explain the following facts, giving reasons.
The wave theory of light could not explain the existence of the threshold frequency.

In the case of photoelectric effect experiment, explain the following facts, giving reasons.
The photoelectric current increases with increase of intensity of incident light.

Define the term: stopping potential in the photoelectric effect.

Explain how does (i) photoelectric current and (ii) kinetic energy of the photoelectrons emitted in a photocell vary if the frequency of incident radiation is doubled, but keeping the intensity same?

Show the graphical variation in the above two cases.