Current Electricity — Physics STD 12 Science — Question

Assertion :   The threshold frequency of photoelectric effect supports the particle nature of sunlight.

Reason      : If frequency of incident light is less than the threshold frequency, electrons are not emitted from metal surface.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

In the circuit shown below the resistance of the galvanometer is 20 W.  In which case of the following alternatives are the currents arranged strictly in the decreasing order

(a) i, i1, i2, ig

(b) i, i2, i1, ig

(c) i, i2, ig, i1

(d) i, i1, ig, i2

In which of the following systems will the radius of the first orbit (n = 1) be minimum?

1. Hydrogen atom.
2. Deuterium atom.
3. Singly ionized helium.
4. Doubly ionized lithium.

A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if.

Electrostatic is the branch of physics which deals with the:

Two files lines can ____.

Magnetic induction is a

(a) Scalar quantity

(b) Vector quantity

(c) Both (a) and (b)

(d) None of the above

Dark lines on solar spectrum are due to

(a) Lack of certain elements

(b) Black body radiation

(c) Absorption of certain wavelengths by outer layers

(d) Scattering

The energy of electron in first excited state of H-atom is  -3.4 eV  its kinetic energy is

(a) – 3.4 eV

(b) + 3.4 eV

(c) – 6.8 eV

(d) 6.8 eV