Science (English Medium) कक्षा १२ - CBSE Important Questions

Use de-Broglie's hypothesis to write the relation for the n^th radius of Bohr orbit in terms of Bohr's quantization condition of orbital angular momentum ?

Plot a graph showing the variation of photoelectric current with intensity of light. The work function for the following metals is given:
Na: 2.75 eV and Mo : 4.175 eV.
Which of these will not give photoelectron emission from a radiation of wavelength 3300

\[A^\circ\] from a laser beam? What happens if the source of laser beam is brought closer?

Define the term "cut off frequency" in photoelectric emission. The threshod frequency of a metal is f. When the light of frequency 2f is incident on the metal plate, the maximum velocity of photo-electrons is v₁. When the frequency of the incident radiation is increased to 5f, the maximum velocity of phto-electrons is v₂. Find the ratio v₁ : v₂.

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.

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).