Nuclei — Physics STD 12 Science — Question

According to Huygens, the ether medium pervading entire universe is:

Why is the screen of the cathode ray tube coated ? Name the material used for coating:

The resistivity of iron is 1 . The resistance of a iron wire of particular length and thickness is 1 ohm. If the length and the diameter of wire both are doubled, then the resistivity in ohm - m  will be

(a)

(b) 2

(c) 4

(d) 8

In a P-type semiconductor

(a) Current is mainly carried by holes

(b) Current is mainly carried by electrons

(c) The material is always positively charged

(d) Doping is done by pentavalent material

Fermi level of energy of an intrinsic semiconductor lies

(a) In the middle of forbidden gap	(b) Below the middle of forbidden gap
(c) Above the middle of forbidden gap	(d) Outside the forbidden gap

When a dielectric material is introduced between the plates of a charged condenser then electric field between the plates

(a) Decreases

(b) Increases

(c) Remain constant

(d) First (b) then (a)

1 milli coulomb =

When a plane mirror is rotated through an angle θ then the reflected ray turns through the angle 2θ then the size of the image

(a) Is doubled

(b) Is halved

(c) Remains the same

(d) Becomes infinite

A bulb of 100 watt is hanging at a height of one meter above the centre of a circular table of diameter 4 m. If the intensity at a point on its rim is , then the intensity at the centre of the table will be

(a)

(b) 2

(c) 2

(d) 5

An astronaut in a spaceship see the outer space as

(a) White

(b) Black

(c) Blue

(d) Red