Tag: physics

Questions Related to physics

What proves that light is a transverse wave?

polarisation of light polarisation wave optics optics physics

  1. Polarization

  2. Reflection

  3. Refraction

  4. Interference

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Correct Option: A
Explanation:

A transverse wave is a wave that oscillates perpendicular to its direction of propagation.  Polarization of light proved that light is a transverse wave.

The helical structures of nucleic acids can be studied by using :

polarisation of light polarisation wave optics optics physics

  1. Interference phenomenon

  2. Diffraction pattern

  3. Polarised light

  4. Photoelectric effect

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Correct Option: C
Explanation:

Polarised light is used to studied helical structures of nucleic acids using different methods such as optical rotatory dispersion. In this method due to refractive indices of the medium for left and right circularly polarised light reflects the structural details of such molecular complexes.

In the light emerging from calcite crystal :

polarisation of light polarisation wave optics optics physics

  1. Both O-ray and E-ray are partially polarised

  2. Both O-ray and E-ray are completely polarised

  3. O-ray is partially polarised and E-ray is completely polarised.

  4. O-ray is completely polarised and E-ray is partially polarised.

Show answer
Correct Option: B
Explanation:

Because of birefringence the ordinary and extra ordinary ray are completely polarized.

In double refraction :

polarisation of light polarisation wave optics optics physics

  1. the velocity of the E-ray varies with direction

  2. e-ray does not obey Snell's law

  3. $\mu $ of E-ray is constant

  4. both A and B

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Correct Option: D
Explanation:

Because the speed of light waves in a medium is equal to their speed in a vacuum divided by the index of refraction for that wavelength, an extra ordinary ray can be either faster or slower than an ordinary ray. The extra ordinary ray does not obey snell's law. It is because refractive index of the e-ray varies according to the direction taken because it has components that are both parallel and perpendicular to the crystal's optic axis.

In double refraction, the stationary image can be produced by :

polarisation of light polarisation wave optics optics physics

  1. O-ray

  2. E-ray

  3. Both O-ray and E-ray combined together

  4. Some times O-ray and some times E-ray

Show answer
Correct Option: A
Explanation:

Only for the ordinary ray the refractive index is observed to be constant in all directions

Consider the following statements A and B. Identify the correct statements.
(A) Polarized light can be used to study the helical structure of nucleic acids.
(B) Optical axis is a direction and not any particular line in the crystal.

polarisation of light polarisation wave optics optics physics

  1. A and B are correct

  2. A and B are wrong

  3. A is correct and B is wrong

  4. A is wrong and B is correct

Show answer
Correct Option: A
Explanation:

Nucleic acid is an optically active medium. When circularly polarized light passes through an absorbing optically active medium, the speeds between right and left polarizations differ as well as their wavelengths. This can be used to study the helical structure of nucleic acids.
An optical axis is a line along which there is some degree of rotational symmetry in an optical system. Thus it is a particular direction and not any
random line.

When unpolarised light passes through a Polaroid sheet the beam that emerges from it is plane polarized. This is due to selective :

polarisation of light polarisation wave optics optics physics

  1. absorption of the O-Ray

  2. absorption of the E-Ray

  3. absorption of the E & O Rays

  4. reflection of one of the rays

Show answer
Correct Option: A
Explanation:

polaroid has absorption of O- Ray as the phenomenon behind its polarising ability.

The Polaroid is :

polarisation of light polarisation wave optics optics physics

  1. Celluloid film

  2. Big crystal

  3. Cluster of small crystal arranged in a regular way

  4. Cluster of small crystals arranged in a haphazard way

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Correct Option: C
Explanation:

Polaroid consists of needle - like crystals aligned in a particular direction.
Thus option C is correct answer.

A calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite, one will see : 

polarisation of light polarisation wave optics optics physics

  1. One dot

  2. Two stationary dots

  3. Two rotating dots

  4. One dot rotating about the other

Show answer
Correct Option: D
Explanation:

calcite crystal display an optical property called birefringence. This causes objects viewed through a clear piece of calcite to appear doubled.
This is the reason one will see one dot rotating about the other.

Consider the following statements A & B. Identify the correct choice in the given answers.
(A) The refractive Index of the extra-ordinary ray depends on the angle of incidence in double refraction
(B) The vibrations of light waves acquire onesidedness for both ordinary and extraordinary rays in double refraction

polarisation of light polarisation wave optics optics physics

  1. A & B are wrong

  2. A & B are correct

  3. A is correct B is wrong

  4. A is wrong B is correct

Show answer
Correct Option: B
Explanation:

In double - refraction the refractive index of the extra - ordinary ray varies according to the direction taken because it has components that  are both parallel and perpendicular to the crystal's optic axis. Thus (A) is correct.
The ordinary ray and the extraordinary ray are polarized in planes vibrating at right angles to each other. Thus (B) is correct.