Electromagnetic Waves — Physics STD 12 Science — Question

The materials suitable for making electromagnets should have:

Penetrating power of X-rays does not depend on

(a) Wavelength	(b) Energy
(c) Potential difference	(d) Current in the filament

The Bohr model of atoms            

(a) Assumes that the angular momentum of electrons is quantized

(b) Uses Einstein’s photo-electric equation

(c) Predicts continuous emission spectra for atoms

(d) Predicts the same emission spectra for all types of atoms

If a slab of insulating material 4   thick is introduced between the plates of a parallel plate capacitor, the separation between plates has to be increased by 3.5   to restore the capacity to original value. The dielectric constant of the material will be

(a) 6

(b) 8

(c) 10

(d) 12

The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become

(a) Twice its original value	(b) Four times its original value
(c) Half its original value	(d) One-fourth its original value

Assertion :  The refractive index of diamond is  and that of liquid is . If the light travels from diamond to the liquid, it will totally reflected when the angle of incidence is 30^o.

Reason    :  μ =  where m is the refractive index of diamond with respect to liquid.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

An electron makes a transition from orbit n = 4 to the orbit n = 2 of a hydrogen atom. The wave number of the emitted radiations (R = Rydberg's constant) will be

(a)

(b)

(c)

(d)

The diffraction effect can be observed in

(a) Only sound waves	(b) Only light waves
(c) Only ultrasonic waves	(d) Sound as well as light waves

Radioactivity is

(a) Irreversible process	(b) Self disintegration process
(c) Spontaneous process	(d) All of the above

Transformers are used:

1. In DC circuits only.
2. In AC circuits only.
3. In both DC and AC circuits.
4. Neither in DC nor in AC circuits.