Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Continuous spectrum is not due to

(a) Hydrogen flame	(b) Electric bulb
(c) Kerosene oil lamp flame	(d) Candle flame

A non.monochromatic light is used in an experiment on photoelectric effect. The stopping potential:

An electric heater of resistance 6 ohm is run for 10 minutes on a 120 volt line. The energy liberated in this period of time is

(a) 7.2

(b) 14.4

(c) 43.2

(d) 28.8

The half life of a radioactive element which has only   of its original mass left after a lapse of 60 days is

(a) 12 days

(b) 32 days

(c) 60 days

(d) 64 days

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

Two electric charges 12μC and -6 μC  are placed 20 cm apart in air. There will be a point P on the line joining these charges and outside the region between them, at which the electric potential is zero. The distance of P from -6 μC  charge is

(a) 0.10 m

(b) 0.15 m

(c) 0.20 m

(d) 0.25 m

According to Einstein's interpretation of the photoelectric effect, the maximum K.E. of photoelectrons depends on ( h -W) where is the frequency of incident radiation and W is the work function. For three different metals graph plotted between maximum K/E. and the frequency of incident radiations. The three graphs obtained: 

The binding energy of nucleus is a measure of its

(a) Charge

(b) Mass

(c) Momentum

(d) Stability

Electroscope is used:

If particles are moving with same velocity, then maximum de-Broglie wavelength will be for

(a) Neutron

(b) Proton

(c) b-particle

(d) α - particle