Ray Optics and Optical Instruments — Physics STD 12 Science — Question

An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used, same water boils in 10 minutes. If the two coils, connected in parallel are used simultaneously, the same water will boil in time

(a) 3 min 20 sec

(b) 5 min

(c) 7 min 30 sec

(d) 2 min 30 sec

Visible light passing through a circular hole forms a diffraction disc of radius 0.1mm on a screen. If an X-ray is passed through the same setup, the radius of the diffraction disc will be:

The transverse nature of light is shown by

(a) Interference of light

(b) Refraction of light

(c) Polarisation of light

(d) Dispersion of light

Earth's electric potential is considered:

The mass of a particle is 400 times than that of an electron and the charge is double. The particle is accelerated by 5 V. Initially the particle remained in rest, then its final kinetic energy will be

(a) 5 eV

(b) 10 eV

(c) 100 eV

(d) 2000 eV

The direction of magnetic lines of forces close to a straight conductor carrying current will be

(a) Along the length of the conductor

(a) Along the length of the conductor

(c) Circular in a plane perpendicular to the conductor

(d) Helical

For the stability of radiated nucleus:

Electroplating does not help in

(a) Fine finish to the surface	(b) Shining appearance
(c) Metals to become hard	(d) Protect metal against corrosion

A monochromatic beam of light passes from a denser medium into a rarer medium. As a result

(a) Its velocity increases	(b) Its velocity decreases
(c) Its frequency decreases	(d) Its wavelength decreases