Electric Charges and Fields — Physics STD 12 Science — Question

Consider the following statements A to B  and identify the correct answer

A. Polarised light can be used to study the helical surface of nucleic acids.

B. Optics axis is a direction and not any particular line in the crystal

(a) A and B are correct	(b) A and B are wrong
(c) A is correct but B is wrong	(d) A is wrong but B is correct

In a single slit diffraction experiment first minimum for red light (660 nm) coincides with first maximum of some other wavelength l'. The value of l' is

(a) 4400 Å

(b) 6600 Å

(c) 2000 Å

(d) 3500 Å

Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact convex. The effective power of the combination is

(a) 45 dioptres

(b) 9 dioptres

(c) 1/9 dioptre

(d) 6 dioptres

Electric room radiator which operates at 225 volts has resistance of 50 ohms. Power of the radiator is approximately

(a) 100 W

(b) 450 W

(c) 750 W

(d) 1000 W

Resistance of semiconductor at 0 K  is

(a) Zero

(b) Infinite

(c) Large

(d) Small

 Identify the electromagnetic wave which is also known as heatwaves.

If the mass number of an atom is A = 40 and its electron configuration is  , the number of neutrons and protons in its nucleus will be

(a) 22, 18

(b) 18, 22

(c) 20, 20

(d) 18, 18

A achromatic combination is made with a lens of focal length f and dispersive power ω with a lens having dispersive power of 2ω. The focal length of second will be

(a) 2f

(b) f/2

(c) -f/2

(d) – 2 f

Li nucleus has three protons and four neutrons. Mass of lithium nucleus is 7.03.6005 amu. Mass of proton is 1.007277 amu and mass of neutron is 1.008665 amu. Mass defect for lithium nucleus in amu is:

According to Bohr, only those states are stable, in which angular momentum of electron will be :