Electric Charges and Fields — Physics STD 12 Science — Question

The critical angle of a medium with respect to air is 45°. The refractive index of medium is

(a) 1.41

(b) 1.2

(c) 1.5

(d) 2

A tuning fork of frequency 480Hz is used to vibrate a sonometer wire having natural frequency 240Hz. The wire will vibrate with a frequency of:

1. 240Hz
2. 480Hz
3. 720Hz
4. Will not vibrate.

Resistance of capacitor for high frequency is:

A uniform spherical shell gradually shrinks maintaining its shape. The gravitational potential at the centre:

1. Increases.
2. Decreases.
3. Remains constant.
4. Oscillates.

The eye can detect 5 × 10⁴ photons per square metre per sec of green light (l = 5000 Å) while the ear can detect  . The factor by which the eye is more sensitive as a power detector than the ear is close to

(a) 5

(b) 10

(c) 106

(d) 15

When electron changes its orbit from outer to inner energy is:

According to Bohr's theory, the expressions for the kinetic and potential energy of an electron revolving in an orbit is given respectively by

(a) +  and	(b) + and
(c)  and	(d)  +  and +

Soap bubbles appear colored when seen in white light. The reason for this phenomenon is :

Emf is most closely related to

(a) Mechanical force	(b) Potential difference
(c) Electric field	(d) Magnetic field