Electric Charges and Fields — Physics STD 12 Science — Question

Monica wanted to take photographs of a monument. But since the surrounding is filled with smoke, she is not able to take good photos. Which one of the following electromagnetic waves can be used in this situation to help Monica?

A condenser of capacity  50μF is charged to 10 volts. Its energy is equal to

(a) 2.5

(b) 2.5

(c) 5

(d) 1.2

Which of the transitions in hydrogen atom emits a photon of lowest frequency  (n = quantum number)

(a) n = 2 to n = 1

(b) n = 4 to n = 3

(c) n = 3 to n = 1

(d) n = 4 to n = 2

The relative atomic masses of many elements are not whole numbers because:

When the current i is flowing through a conductor, the drift velocity is v. If  2i  current is flowed through the same metal but having double the area of cross-section, then the drift velocity will be

(a) v/4

(b) v/2

(c) v

(d) 4v

The output of a 2-input OR gate is zero only when its:

A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side on its principal axis, the intensity of light:

1. Remains, constant.
2. Continuously increases.
3. Continuously decreases.
4. First increases then decreases.

Four resistances are connected in a circuit in the given figure. The electric current flowing through 4 ohm and 6 ohm resistance is respectively

(a)  2 amp and 4 amp	(b) 1 amp and 2 amp
(c) 1 amp and 1 amp	(d) 2 amp and 2 amp

A radio transmitter radiates 1 kW power at a wavelength 198.6 metres. How many photons does it emit per second

(a)

(b)

(c)

(d)