# CBSE Class 12 Physics Sample Paper 2020 Solved (3)

CBSE Class 12 Physics Sample Paper 2020 Solved (3). It’s always recommended to practice as many sample papers as possible before the examinations. Students can download the sample papers and also question papers of previous years to practice and score better marks in examinations. Refer to other links too for more sample papers.

SECTION A

1. A charge Q is distributed over a metal sphere of radius R. What is the electric field and electric potential at the centre?

2. V – I graph for a metallic wire at two different temperatures T1 and T2 is as shown in the figure. Which of the two temperatures is higher and why?

3. Show graphically the variation of magnetic field due to a straight conductor of uniform cross-section of radius ‘a’ and carrying steady currently as a function of distance r (a > r) from the axis of the conductor.

4. When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the colour of light?

5. What is the function of a band pass filter used in a modulator for obtaining AM signal?

SECTION B

6. Draw a graph to show the temperature dependency of resistivity for a typical semiconductor and alloy.

7. When the electron orbiting in hydrogen atom in its ground state moves to the third excited state, show how the de Broglie wavelength associated with it would be affected.

8. Define a wavefront. Using Huygens’ Principle, draw the shape of a refracted wavefront, when a plane wave is incident on a convex lens.

OR

(a) When a wave is propagating from a rarer to a denser medium, which characteristic of the wave does not change and why?

(b) What is the ratio of the velocity of the wave in the two media of refractive indices μ1 and μ2?

9. Distinguish between point to point and broadcast communication modes. Give one example of each.

10. From the relation R = R0 A1/3 where R0 is a constant and A is the mass number of a nucleus, show that nuclear matter density is nearly constant.

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