Electrostatics — Physics STD 12 Science — Question

If the wavelength of red light in air is 7500 A, then the frequency of light in air is.

A 10 ohm electric heater operates on a 110 V line. Calculate the rate at which it develops heat in watts

(a) 1310 W

(b) 670 W

(c) 810 W

(d) 1210 W

Which of the following electromagnetic waves have minimum frequency

(a) Microwaves

(b) Audible waves

(c) Ultrasonic waves

(d) Radiowaves

According to the Rutherford’s atomic model, the electrons inside the atom are:

Which is not true with respect to the cathode rays

(a) A stream of electrons	(b) Charged particles
(c) Move with speed same as that of light	(d) Can be deflected by magnetic fields

When current is passed in antimony-bismuth couple, then

(a) The junction becomes hot when the current is from bismuth to antimony

(b) The junction becomes hot when current flows from antimony to bismuth

(c) Both junctions become hot

(d) Both junctions become cold

A 2 MeV proton is moving perpendicular to a uniform magnetic field of 2.5 tesla. The force on the proton is

(a) 2.5

(b) 7.6

(c) 2.5

(d) 7.6

In a hydrogen discharge tube it is observed that through a given cross-section 3.13   electrons are moving from right to left and 3.12  protons are moving from left to right. What is the electric current in the discharge tube and what is its direction

(a) 1 mA towards right	(b) 1mA towards left
(c) 2mA towards left	(d) 2mA towards right

When radiation of wavelength   is incident on a metallic surface, the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts. Then the threshold wavelength for the surface is

(a) 2

(b) 4

(c) 6

(d) 8

At a certain place a magnet makes 30 oscillations per minute. At another place where the magnetic field is double, its time period will be

(a) 4 sec

(b) 2 sec

(c)

(d)