Electromagnetic Waves — Physics STD 12 Science — Question

When a metal surface is illuminated by light of wavelengths 400 nm and 250 nm, the maximum velocities of the photoelectrons ejected are  v and 2v respectively. The work function of the metal is (h = Planck’s constant, c = velocity of light in air)

(a) 2hc

(b)

(c)

(d) 0.5

A charge q is placed at the centre of the open end of a cylindrical vessel (figure). The flux of the electric field through the surface of the vessel is:

In the propagation of electromagnetic waves the angle between the direction of propagation and plane of polarisation is

(a) 0o

(b) 45o

(c) 90o

(d) 180o

A radioactive material has a half-life of 8 years. The activity of the material will decrease to about 1/8 of its original value in

(a) 256 year

(b) 128 year

(c) 64 year

(d) 24 year

When there is an electric current through a conducting wire along its length, then an electric field must exist

(a)  Outside the wire but normal to it	(b) Outside the wire but parallel to it
(c) Inside the wire but parallel to it	(d) Inside the wire but normal to it

In an experiment of meter bridge, a null point is obtained at the centre of the bridge wire. When a resistance of 10 ohm is connected in one gap, the value of resistance in other gap is

(a) 10 Ω

(b) 5 Ω

(c)

(d) 500 Ω

Which of the planet is brightest

(a) Mercury

(b) Venus

(c) Mars

(d) Jupiter

When a potential difference is applied across, the current passing through

(a) An insulator at 0 K  is zero

(b) A semiconductor at 0 K  is zero

(c) A P-N diode at 300 K  is finite, if it is reverse biased

(d) a, b, c

A capacitor is a system of two conductors separated by _____.