Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

A proton and an electron have same kinetic. Which one has greater de-Broglie wavelength and why?

A proton and an electron have same velocity. Which one has greater de-Broglie wavelength and why?

Define the term ‘stopping potential’ in relation to photo-electric effect.

Using de Broglie’s hypothesis, explain with the help of a suitable diagram, Bohr’s second postulate of quantization of energy levels in a hydrogen atom.

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.

An electron is accelerated through a potential difference of 64 volts. What is the de-Broglie wavelength associated with it? To which part of the electromagnetic spectrum does this value of wavelength correspond?

An electron, an alpha particle and a proton have the same kinetic energy.

Which one of these particles has the largest de-Broglie wavelength? 

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).

Answer the following question.
Obtain the expression for the ratio of the de-Broglie wavelengths associated with the electron orbiting in the second and third excited states of the hydrogen atom.

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.