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

The resistance of a metal increases with increasing temperature because:

Three photons coming from excited atomic-hydrogen sample are picked up. Their energies are 12.1eV, 10.2 eV and 1.9eV. These photons must come from:

A conducting disc of radius r spins about its axis with an angular velocity ω. There is a uniform magnetic field of magnetude B perpendicular to the plane of the disc. C is the centre of the ring.

Which of the following transition will have highest emission wavelength(a) n = 2 to  n = 1 (b) n = 1 to n = 2 (c) n = 2 to n= 5 (d) n = 5 to n = 2

A charge of 5C  experiences a force of 5000 N when it is kept in a uniform electric field. What is the potential difference between two points separated by a distance of 1 cm (a) 10 V(b) 250 V (c) 1000 V (d) 2500 V

An example of a diamagnetic substance is(a) Aluminium(b) Copper(c) Iron   (d) Nickel

Which of the following are insulators.

Huygen’s principle of secondary wavelets may be used to(a) Find the velocity of light in vacuum (b) Explain the particle behaviour of light(c) Find the new position of the wavefront(d) Explain photoelectric effect

The velocity factor of a transmission line x. If dielectric constant of the medium is 2.6, the value of x is(a) 0.26(b) 0.62(c) 2.6(d) 6.2