PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions

An amplitude modulated (AM) radio wave bends appreciably round the corners of a 1 m × 1 m board but a frequency modulated (FM) wave only bends negligibly. If the average wavelengths of the AM and FM waves are \[\lambda_a   and   \lambda_f,\]

The inverse square law of intensity \[\left(\text{i.e. the intensity }\infty \frac{1}{r^2}\right)\] is valid for a ____________ .

A light wave can travel

(a) in vacuum

(b) in vacuum only

(c) in a material medium

(d) in a material medium only

Which of the following properties of light conclusively support the wave theory of light?

(a) Light obeys the laws of reflection.

(b) Speed of light in water is smaller than its speed in vacuum.

(c) Light shows interference.

(d) Light shows photoelectric effect.

When light propagates in vacuum, there is an electric field as well as a magnetic field. These fields ____________ .

(a) are constant in time

(b) have zero average value

(c) are perpendicular to the direction of propagation of light.

(d) are mutually perpendicular

Three observers A, B and C measure the speed of light coming from a source to be ν_A, ν_Band ν_C. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is vacuum everywhere.

(a) \[\nu_A  >  \nu_B  >  \nu_C\]

(b) \[\nu_A  <  \nu_B  <  \nu_C\]

(c) \[\nu_A  =  \nu_B  =  \nu_C\]

(d) \[\nu_B  = \frac{1}{2}\left( \nu_A + \nu_C \right)\]

Three observers A, B and C measure the speed of light coming from a source to be ν_A, ν_Band ν_C. A moves towards the source and C moves away from the source at the same speed. B remains stationary. The surrounding space is water everywhere.

(a) \[\nu_A  >  \nu_B  >  \nu_C\]

(b) \[\nu_A  <  \nu_B  <  \nu_C\]

(c) \[\nu_A  =  \nu_B  =  \nu_C\]

(d) \[\nu_B  = \frac{1}{2}\left( \nu_A + \nu_C \right)\]

Find the range of frequency of light that is visible to an average human being

\[\left( 400\text{ nm }< \lambda < 700\text{ nm}\right)\]

The wavelength of sodium light in air is 589 nm. (a) Find its frequency in air. (b) Find its wavelength in water (refractive index = 1.33). (c) Find its frequency in water. (d) Find its speed in water.

The speed of yellow light in a certain liquid is 2.4 × 10⁸ m s⁻¹. Find the refractive index of the liquid.

Two narrow slits emitting light in phase are separated by a distance of 1⋅0 cm. The wavelength of the light is \[5 \cdot 0 \times  {10}^{- 7} m.\] The interference pattern is observed on a screen placed at a distance of 1.0 m. (a) Find the separation between consecutive maxima. Can you expect to distinguish between these maxima? (b) Find the separation between the sources which will give a separation of 1.0 mm between consecutive maxima.

Find the thickness of a plate which will produce a change in optical path equal to half the wavelength λ of the light passing through it normally. The refractive index of the plate is μ.

A parallel beam of light of wavelength 560 nm falls on a thin film of oil (refractive index = 1.4). What should be the minimum thickness of the film so that it strongly reflects the light?

A parallel beam of white light is incident normally on a water film 1.0 × 10⁻⁴ cm thick. Find the wavelengths in the visible range (400 nm − 700 nm) which are strongly transmitted by the film. Refractive index of water = 1.33.

A glass surface is coated by an oil film of uniform thickness 1.00 × 10⁻⁴ cm. The index of refraction of the oil is 1.25 and that of the glass is 1.50. Find the wavelengths of light in the visible region (400 nm − 750 nm) which are completely transmitted by the oil film under normal incidence.

Plane microwaves are incident on a long slit of width 5.0 cm. Calculate the wavelength of the microwaves if the first diffraction minimum is formed at θ = 30°.

Why does a compass needle get deflected when brought near a bar magnet?

A double convex lens is made of a glass of refractive index 1.55, with both faces of the same radius of curvature. Find the radius of curvature required, if the focal length is 20 cm.

A circular coil of cross-sectional area 200 cm² and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s⁻¹ in a uniform magnetic field of magnitude 3.0 × 10⁻²T. Calculate the maximum value of the current in the coil.

Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.