Set A class XII-A Physics Q1- Q4 1marks each Q5- Q18 2marks each Q19- Q29 3marks each Q30- 5 marks

1. How does the dispersive power of glass prism change when it is dipped in water? 2. What is the rest mass of photon?

3. Write the relation between number density of holes and number density of free electrons in an intrinsic

semiconductor.

4. Write the value of resistance offered by an ideal diode when (i) forward based (ii) reverse biased.

5. If the frequency of the input signal is f. What will be the frequency of the pulsating output signal

in case of: (i) half wave rectifier? (ii) full wave rectifier?

6. Find the equivalent resistance of the network shown in figure between point A and B when the

p-n junction diode is ideal and :(i) A is at higher potential (ii) B is at higher potential

7. Potential barrier of p.n. junction cannot be measured by connecting a sensitive voltmeter across

its terminals. Why?

8. Write two differences between point to point communication and broadcast mode of communication. Give one

example of each.

9. An audio signal of amplitude one fourth of the carrier wave, is used in amplitude modulation. What is the

modulation index?

10. What are the essential components of a communication system? Explain with the help of a Block diagram.

11. Explain by a diagram, how space waves are used for Television broadcast.

12. Define distance of the closest approach. An -particle of kinetic energy ‘K’ is bombarded on a thin gold foil. The

distance of the closet approach is ‘r’. What will be the distance of closest approach for an -particle of double the

kinetic energy?

13. Show that nuclear density is independent of the mass number.

14. Write one similarity and one difference between matter wave and an electromagnetic wave.

15. Does a photon have a de Broglie wavelength? Explain.

16. A near sighted person can clearly see objects up to a distance of 1.5m. Calculate power of the

lens necessary for the remedy of this defect.

17. Name any two characteristics of light which do not change on polarisation.

18. Complete the path of light with correct value of angle of emergence.

19. Using mirror formula show that virtual image produced by a convex mirror is always smaller in size and is

located between the focus and the pole.

20. Obtain the formula for combined focal length of two thin lenses in contact, taking one divergent and the other

convergent.

21. Derive snell’s law on the basis of Huygen’s wave theory.

22. Explain the working of a photocell? Give its two uses.

23. Find the de Broglie wavelength associated with an electron accelerated through a potential difference V.

24. Give one example of a nuclear reaction. Also define the Q-value of the reaction. What does Q > 0 signify?

25. Explain how radio-active nucleus can-emit β-particles even though nuclei do not contain these

particles. Hence explain why the mass number of radioactive nuclide does not change during β -decay.

26. Define the term half life period and decay constant. Derive the relation between these terms.

27. What is depletion region in p-n junction diode. Explain its formation with the help of a suitable diagram.

28. Explain the working of npn transistor as an amplifier and find an expression for its voltage gain.

29. With the help of Block Diagram show how an amplitude modulated wave can be demodulated.

30. Draw a labelled ray diagram of a compound microscope and explain its working. Derive an expression for its

magnifying power.

OR

Diagrammatically show the phenomenon of refraction through a prism. Define angle of deviation in this case. Hence

for a small angle of incidence derive the relation = (μ – 1) A.