Atoms — Physics STD 12 Science — Question

Assertion  : The surface wave propagation is used for medium wave band and for television broadcasting.

Reason     :  The surface waves travel directly from transmitting antenna to receiver antenna through atmosphere.

(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 Young's double slit experiment how many maximas can be obtained on a screen (including the central maximum) on both sides of the central fringe if λ = 2000 and d = 7000  

(a) 12

(b) 7

(c) 18

(d) 4

The force that a unit positive charge would experiences if placed at that point is called as _____ due to charge at a point in space.

A radioactive material has a half-life of 8 years. The activity of the material will decrease to about 1/8 of its original value in

(a) 256 year

(b) 128 year

(c) 64 year

(d) 24 year

In  nucleus, there are

(a) 138 protons and 88 neutrons	(b) 138 neutrons and 88 protons
(c) 226 protons and 88 electrons	(d) 226 neutrons and 138 electrons

If a small amount of antimony is added to germanium crystal:

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in:

Which of the following relation is significant for metals when the temperature increases?

de-Broglie wavelength of a body of mass m and kinetic energy E is given by

(a)

(b)

(c)

(d)

The number of protons in an atom of atomic number Z and mass number A is: