Physics : Term - II CLASS - XII Time Allowed : 2 Hours Theory Marks : 35
NOTE
1. Question paper has total 17 questions.
2. All questions are compulsory.
3.Q.1 to 5 will carry 1 mark each.
4.Q 6 to 13 will be of 2 marks each. There will be internal choice in two questions.
5.Q.14 to 16 will be of 3 marks. There will be internal choice in two questions
6.Q.17 will be of 5 marks. There will be internal choice in it.
Q 1. A ray incident normally to the mirror retraces its path. Why?
Q 2. How does the focal length of a Convex lens change, if red light is used instead of violet light?
Q 3. How will the photoelectric current change on decreasing the wavelength of the incident
radiation?
Q 4. Name the series of hydrogen atom which lie in UV region.
Q 5. What is meant by doping? (1 x 5 = 5)
Q 6. What do you mean by magnifying power of a microscope ?
Q 7. What is the ratio of the slit widths; if the amplitude ratio of the light waves from them is √3:1?
Or
explain the cause of refraction of light.
Q 8.
A particle with rest mass m, is moving with velocity 'c'. What is the de-Broglie wavelength
associated with it?
Q 9. Complete the given equation : ₉₂U²³⁵+ ₀n¹ → ….
?
Q 10.
State the postulates of Bohr's theory of hydrogen atom.
Q 11.
Draw a relationship between activity ‘A’ and half-life 'T₁/₂.
Q 12. Write the nuclear reactions of the following :-
(i) 𝜶 decay of ₈₄Po²⁰⁴ (ii) 𝛽 decay of ₁₅P³²
Q 13.
A n-type semi-conductor has a large number of electrons but still it is electrically neutral. Explain.
Or
Which semi-conductor has more mobility : p-type or n-type ? Explain.
(2 x 8 = 16)
Q 14 What is total internal reflection? Show that, 𝝁＝1/ SinC. Where 'c' is the critical angle.
Q 15. Using Bohr's postulates of atomic model, derive an expression for radius of nth electron orbit.
Hence obtain the expression for Bohr's radius.
Or
What are the drawbacks of Rutherford atomic model ?
Q 16 Explain how the width of depletion layer in a p-n junction diode changes, when the junction
is.
(i) forward biased, (ii) reverse biased. Explain with the help of diagrams.
Or
What is LED ? Mention two important properties of LED's over conventional lamps. (3 * 3 = 9)
Q17 Prove the mirror formula for a convex lens..
Or
A 6 cm tall object is placed 20cm from a convex mirror of focal-length 10cm. Find the position,
size and nature of the image.
(1 * 5 = 5)
