1. A point charge Q is placed at point ‘O’ as shown in the figure. Is the potential at point A, i.e. VA , greater, smaller or equal to potential, VB , at point B, when Q is (i) positive, and (ii) negative charge ?

 

2. Write the expression for speed of electromagnetic waves in a medium of electrical permittivity  and magnetic permeability .

 

3. Does the magnifying power of a microscope depend on the colour of the light used ? Justify your answer.

 

4. Draw logic symbol of an OR gate and write its truth table.

 

5. A photosensitive surface emits photoelectrons when red light falls on it. Will the surface emit photoelectrons when blue light is incident on it ? Give reason.

 

6. Find the intensity at a point on a screen in Young’s double slit experiment where the interfering waves of equal intensity have a path difference of (i) /4, and (ii) /3.

 

7. Write two points of difference between intrinsic and extrinsic semiconductors.

 

8. Distinguish between broadcast mode and point-to-point mode of communication and give one example for each.

 

9. A light bulb and a solenoid are connected in series across an ac source of voltage. Explain, how the glow of the light bulb will be affected when an
iron rod is inserted in the solenoid.

 

10.Use the mirror equation to show that an object placed between f and 2f of a concave mirror forms an image beyond 2f.
OR
(a) State the condition under which a large magnification can be achieved in an astronomical telescope.
(b) Give two reasons to explain why a reflecting telescope is preferred over a refracting telescope.