Magnetism And Matter — Physics STD 12 Science — Question

When the accelerating voltage applied on the electrons increased beyond a critical value

(a) Only the intensity of the various wavelengths is increased

(b) Only the wavelength of characteristic relation is affected

(c) The spectrum of white radiation is unaffected

(d) The intensities of characteristic lines relative to the white spectrum are increased but there is no change in their wavelength

 If the wavelength of electromagnetic radiation is doubled, what will happen to the energy of photons?

The value of photoelectric current depends :

In a good conductor the energy gap between the conduction band and the valence band is

(a) Infinite

(b) Wide

(c) Narrow

(d) Zero

Which of the following cannot be polarised?

In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is

(a) 4 A

(b) 2 A

(c) 6 A

(d) 10 A

A man wearing glasses of focal length +1m cannot clearly see beyond 1m:

1. If he is farsighted.
2. If he is nearsighted.
3. If his vision is normal.
4. In each of these cases.

Four resistances of 100 W each are connected in the form of square. Then, the effective resistance along the diagonal points is

(a) 200 W

(b) 400 W

(c) 100 W

(d) 150 W

X-rays of wavelength 0.1 Å allowed to fall on a metal get scattered. The wavelength of scattered radiation is 0.111 Å. If h = 6.624 × 10^–34 J-s and m₀ = 9 × 10^–31 kg, then the direction of the scattered photons will be

(a) cos–1 (0.547)

(b) cos–1 (0.4484)

(c) cos–1 (0.5)

(d) cos–1 (0.3)

The energy of hydrogen atom in its ground state is – 13.6 eV. The energy of the level corresponding  to the quantum number n is equal 5 is

(a) – 5.40 eV

(b) – 2.72 eV

(c) – 0.85 eV

(d) – 0.54 eV