Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

If a lens is cut into two pieces perpendicular to the principal axis and only one part is used, the intensity of the image

(a) Remains same

(b)  times

(c) 2 times

(d) Infinite

In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change:

To explain his theory, Bohr used

(a) Conservation of linear momentum

(b) Conservation of angular momentum

(c) Conservation of quantum frequency

(d) Conservation of energy

According to the theory of relativity, all laws of nature are the same in reference frames that::

Earth's electric potential is considered:

The current gain of a transistor in common base mode is 0.995. The current gain of the same transistor in common emitter mode is?

A gamma ray photon creates an electron- positron pair. If the rest mass energy of an electron is 0.5 MeV and the total K.E. of the electron- positron pair is 0.78 MeV, then the energy of the gamma ray photon must be

(a) 0.78 MeV

(b) 1.78 MeV

(c) 1.28 MeV

(d) 0.28 MeV

Assertion   :   Free electron always keep on moving in a conductor even then no magnetic force act on them in magnetic field unless a current is passed through it.

Reason       : The average velocity of free electron is zero.

(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.

The minimum wavelength of X-rays produced in a coolidge tube operated at potential difference of 40 kV is

(a) 0.31 Å

(b) 3.1 Å

(c) 31 Å

(d) 311 Å

Wheatstones’s bridge cannot be used for measurement of very _______ resistances.