61.

The energy of an electron in excited hydrogen atom is −3.4eV. Then according to Bohr's theory, the angular momentum of the electron is

• 2.1 × 10^-34 J-s

• 3 × 10^-34 J-s

• 2 × 10^-34 J-s

• 0.5 × 10^-34 J-s

If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion would

• decrease by a factor 2/3

• decrease by a factor 4/9

• decrease by a factor 5/9

• decrease by a factor $5\sqrt{9}$

A semiconductor has an electron concentration of 8 x 10¹³ /m³ and hole concentration of 5.5 10¹²/m³. The semiconductor is

• n-type

• p-type

• intrinsic semiconductor

• p-n junction

In the figure shown below, which of the diodes are forward biased ?

• 1, 2, 3

• 2, 4, 5

• 1, 3, 4

• 2, 3, 4

Given below are four logic gate symbols . Those for OR, NOR and NAND are respectively

• 1, 4, 3

• 4, 1, 2

• 1, 3, 4

• 4, 2, 1

The albedo of a planet is indicative of its

• transmission coefficient

• reflection coefficient

• absorption coefficient

• adsorption coefficient

Huygen's principle of secondary wavelets may be used to

• find the velocity of light in vacuum

• explain the particle behaviour of light

• find the new position of a wavefront

• explain photoelectric effect

In Young's double slit experiment, the intensity of light coming from one of the slits is double the intensity from the other slit. The ratio of the maximum intensity to the minimum intensity in the interference fringe pattern observed is

• 34

• 40

• 25

• 38

Three observers A, B, C measure the speed of light coming from a source to be v_A, v_B and v_C. The observer A moves away from the source at the same speed. The observer B stays stationary. The surrounding space is vacuum everywhere. Then

• v_A > v_B > v_C

• v_A < v_B < v_C

• v_A = v_B = v_C

• v_A = v_B > v_C

Lumen is the unit of

• luminous flux

• luminosity

• illuminance

• quantity of light