Atoms — Physics STD 12 Science — Question

The X – 1/T graph for an alloy of paramagnetic nature is shown in Fig. The curie constant is, then

(a) 57 K

(b) 2.8

(c) 570 K

(d) 17.5

A plane mirror is approaching you at a speed of 10 cm/sec You can see your image in it. At what speed will your image approach you

(a) 10 cm/sec

(b) 5 cm/sec

(c) 20 cm/sec

(d) 15 cm/sec

If T is the half life of a radioactive material, then the fraction that would remain after a time   is

(a)

(b)

(c)

(d)

Two similar bar magnets P and Q, each of magnetic moment M, are taken, If P is cut along its axial line and Q is cut along its equatorial line, all the four pieces obtained have

(a) Equal pole strength	(b) Magnetic moment
(c) Magnetic moment	(d) Magnetic moment M

A student wants to find if a star if moving away from the earth or towards the earth. Which of the following principle he can use? 

Asteroids are

(a) Small planets	(b) Shooting stars
(c) Found in a belt between Earth ad Venus	(d) None of these

A coil of N turns and mean cross-sectional area A is rotating with uniform angular velocity w about an axis at right angle to uniform magnetic field B. The induced e.m.f. E in the coil will be

(a) NBA sinwt

(b) NB w sinwt

(c) NB/A sinwt

(d) NBA w sinwt

An  object of length 6 cm is placed on the principle axis of a concave mirror of focal length f at a distance of 4f. The length of the image will be

(a) 2 cm

(b) 12 cm

(c) 4 cm

(d) 1.2 cm

Two similar plano-convex lenses are combined together in three different ways as shown in the adjoining figure. The ratio of the focal lengths in three cases will be

(a) 2 : 2 : 1

(b) 1 : 1 : 1

(c) 1 : 2 : 2

(d) 2 : 1 : 1

 Which among the following is an application of microwaves?