ISC (Science) ISC Class 12 - CISCE Question Bank Solutions for Physics (Theory)

In Figure 1 below, a charge Q is fixed. Another charge q is moved along a circular arc MN of radius r around it, from the point M to the point N such that the length of the arc MN = l. The work done in this process is: 

figure 1

If l₃ and l₂ represent angular momenta of an orbiting electron in III and II Bohr orbits respectively, then l₃: l₂ is :

With reference to the photoelectric effect, what is meant by threshold wavelength?

State any one property which is common to all electromagnetic waves.

Two metals A and B have work functions 4 eV and 6 eV respectively. Which metal has a lower threshold wavelength for photoelectric effect?

Calculate angular momentum of an electron in the third Bohr orbit of a hydrogen atom.

Plot a labelled graph of IV_sl where V_s is stopping potential versus frequency f of the incident radiation. 

State how will you use this graph to detennine the value of Planck's constant.

Draw energy level diagram for a hydrogen atom, showing the first four energy levels corresponding to n=1, 2, 3 and 4. Show transitions responsible for:
(i) Absorption spectrum of Lyman series.
(ii) The emission spectrum of the Balmer series.

If the frequency of the incident radiation is increased from 4 × 10¹⁵ Hz to 8 × 10¹⁵ Hz, by how much will the stopping potential for a given photosensitive surface go up?

The energy levels of an atom of a certain element are shown in the given figure. Which one of the transitions A, B, C, D or E will result in the emission of photons of electromagnetic radiation of wavelength 618.75 nm? Support your answer with mathematical calculations.

How are various lines of Lyman series formed? Explain on the basis of Bohr’s theory.

With reference to Semiconductor Physics,

Draw a labelled energy band diagram for a semiconductor.

If the radius of first electron orbit in hydrogen atom be r then the radius of the fourth orbit ill be ______.

The energy of an electron in an excited hydrogen atom is - 3.4 eV. Calculate the angular momentum of the electron according to Bohr's theory. (h = 6.626 × 10^-34 Js)

Using Bohr's postulates derive the expression for the radius of n^th orbit of the electron.

Ratio of longest to shortest wavelength in Balmer series is ______.

Light of wavelength 4000 Å is incident on two metals A and B. Which metal will emit photoelectrons, if their work functions are 3.8 e V and 1.6 e V respectively?

What is forbidden band?

An electric current (I) flowing through a metallic wire is gradually increased. The graph of heating power (P) developed in it versus the current (I) is ______.