Polarisation MCQ Quiz - Objective Question with Answer for Polarisation - Download Free PDF
Last updated on May 20, 2025
Latest Polarisation MCQ Objective Questions
Polarisation Question 1:
The intensity of transmitted light when a polaroid sheet, placed between two crossed polarization at 22.5° from the polarization axis of one of the polaroids, is (I₀ is the intensity or polarised light after passing through the first polaroid):
Answer (Detailed Solution Below)
Polarisation Question 1 Detailed Solution
When light passes through a polaroid at an angle θ from the original polarization direction, the transmitted intensity is given by:
I = I0 × cos²θ
Since there are two polaroids with one in between at 22.5°, the intensity after the first polaroid becomes I0.
After the second polaroid (placed at 22.5° to the first):
I1 = I0 × cos²(22.5°)
After the third polaroid (crossed with the first, i.e., 90° apart, and thus 67.5° from the middle one):
I2 = I1 × cos²(67.5°)
So final intensity = I0 × cos²(22.5°) × cos²(67.5°)
cos(22.5°) ≈ 0.924, cos²(22.5°) ≈ 0.853
cos(67.5°) ≈ 0.383, cos²(67.5°) ≈ 0.146
Final intensity ≈ I0 × 0.853 × 0.146 ≈ I0 × 0.124 ≈ I0 / 8
Correct option: Option 3 (I0 / 8)
Polarisation Question 2:
Match the following optical phenomenon with the respective application :
a) Total internal reflection |
e) Optical activity of crystals |
b) Interference |
f) Structure of crystals |
c) Diffraction |
g) Flatness of surfaces |
d) Polarisation |
h) Optical fibres |
Answer (Detailed Solution Below)
Polarisation Question 2 Detailed Solution
CONCEPT:
- Total Internal reflection: The total reflection of light from a higher refractive index medium to back in its medium at an angle more than a critical angle known as total internal reflection.
- It always happens when light travels from denser medium to rarer medium.
- Optical fibre: It is a very thin fibre made of glass and plastic having a radius of the order of a micrometre (10-6 m).
- It works on the principle of Total Internal Reflection.
- It is lightweight, fast, and useful for long-distance data and light transmission with very few losses.
- A bundle of such thin fibres forms a light pipe.
- Interference: The combination of two or more electromagnetic waveforms to form a resultant wave that may have greater, lower, or the same amplitude is called interference.
- There is an experimental observation for measurement of the flatness of the surface by using the interference phenomenon.
- Diffraction: It is defined as bending of waves around the corner when a wave encounters an obstacle.
- For the structure of a crystal, we use the diffraction phenomenon to see how much the light is diffracted by it.
- Polarization: It is a property of transverse waves. The direction of oscillations becomes perpendicular to the direction of motion
- Light passing through a calcite crystal is split into two rays. The two rays of light are each plane-polarized by the calcite such that the planes of polarization are mutually perpendicular.
The optical activity of the above crystal is measured by the polarization phenomenon.
EXPLANATION:
From the above discussion,
we can match: a-h, b-g, c-f, d-e
So option 2 is correct.
Polarisation Question 3:
A point source S emits unpolarized light uniformly in all directions. At two points A and B, the ratio r = IA/IB of the intensities of light is 2. If a set of two polaroids having 45° angle between their pass-axes is placed just before point B, then the new value of r will be _____.
Answer (Detailed Solution Below) 8
Polarisation Question 3 Detailed Solution
Calculation:
Where I : distance from point source
⇒
⇒
Also, due to polaroids:
⇒
⇒ Ratio becomes 4 times.
⇒ rnew = 8
Polarisation Question 4:
A beam of unpolarised light of intensity
Answer (Detailed Solution Below)
Polarisation Question 4 Detailed Solution
For unpolarised light, it can be resolved into two components of equal magnitude in any pair of perpendicular directions. So the amplitude that is along the plane of polarisation of the polaroid will always be
So, the intensity which will pass through it will always be
Now when this polarised light falls on polaroid B whose plane of polarisation makes an angle
Therefore, intensity of light that passes through is
Here,
So intensity of light emerging through B is
Polarisation Question 5:
The polaroids are placed in the path of unpolarized beam of intensity
Answer (Detailed Solution Below)
Polarisation Question 5 Detailed Solution
No light is emitted from the second polariod, so
Let the initial intensity of light is
Intensity of light emitted from
Intensity of light transmitted from last polaroid i.e. from
Top Polarisation MCQ Objective Questions
A ray of light passes from medium X to another medium Y. If no refraction occurs then the angle between incident light and surface of medium Y should be
Answer (Detailed Solution Below)
Polarisation Question 6 Detailed Solution
Download Solution PDFThe correct answer is 90°.
If no refraction occurs when a ray of light passes from medium X to medium Y, it means that the light ray is incident at an angle such that it does not bend upon entering the new medium. For this to happen, the light must strike the boundary between the two media perpendicularly.
Explanation:
- If a light is incident at an angle of 90°, it will go straight again, making an angle of 90° with the normal; the medium has no effect.
- As a result, the angle of incidence is 90°.
- If an angle of incidence is 90°, it means the light is propagating along the interface separating the two media.
- In this case, the light does not enter the second medium and so we can not talk about the angle of refraction.
- The angle of refraction can also be regarded as 90°.
Thus, A ray of light passes from medium X to another medium Y. If no refraction occurs then the angle between incident light and surface of medium Y should be 90°.
Which of the following phenomena is not common in light and sound wave?
Answer (Detailed Solution Below)
Polarisation Question 7 Detailed Solution
Download Solution PDFCONCEPT:
Sound:
- A sound is a form of energy that produces a sensation of hearing in our ears.
- It is a kind of disturbance that travels through a medium due to repeated vibrations of the particles of the medium about their mean positions.
- The disturbance being handed over from one particle to the next.
Light:
- Light is a form of electromagnetic radiation that can be detected by the human eye.
- When light falls on an object, some part of the light is reflected on our eyes and we are able to see.
EXPLANATION:
- Sound waves are longitudinal waves and light waves are transverse waves.
- As we know sound waves are longitudinal waves and travel through compression and refractions in the medium on the other hand light waves are transverse in nature and do not require a medium to travel.
- As we know that, the sound wave and lightwave travels with different velocity and have a different frequency, therefore the wavelength (λ = v/f) is different for both.
- Both sound and light waves follow the law of reflection, refraction, and interference of waves.
- Polarization occurs with light waves only.
When a beam of ordinary light is passed through a calcite crystal, the light splits into O-ray and E-ray inside the crystal.
Answer (Detailed Solution Below)
Polarisation Question 8 Detailed Solution
Download Solution PDFWhen ordinary light is allowed to pass through calcite or quartz, it splits into two refracted beams(O-ray & E –ray) and both are plane-polarized lights.
Polarisation:
- The phenomenon due to which vibrations of light waves are restricted in a particular plane is called polarisation.
- In an ordinary beam of light from a source, the vibrations occur normal to the direction of propagation in all possible planes. Such a beam of light called unpolarised light.
- If by some methods (reflection, refraction, or scattering) a beam of light is produced in which vibrations are confined to only one plane, then it is called plane polarised light.
- Hence, polarization is the phenomenon of producing plane polarised light from unpolarised light.
Additional Information
There are three types of polarized light
- Plane Polarized Light
- Circularly Polarized Light (O-ray)
- Elliptically Polarized Light (E-ray)
The critical angle of glass w.r.t air is 35.26o. What is the angle of refraction for light, incident on glass at polarization angle? (sin 35.26o = 0.577)
Answer (Detailed Solution Below)
Polarisation Question 9 Detailed Solution
Download Solution PDFConcept:
The angle of incidence at which a beam of unpolarized light falling on a transparent surface is reflected as a beam of completely plane polarised light is called polarising or Brewster angle. It is denoted by ip.
Brewster's law: It states that when a ray is passed through some transparent medium having refractive index μ at any particular angle of incidence, reflected ray is completely polarized; and the angle between reflected and refracted ray is 900.
μ = tan θB
Where μ = refractive index and θB is Brewster's angle or polarizing angle (ip).
Critical angle: When a ray of light is going from a denser medium to a rare medium then the angle of incidence at which the refraction angle is 90° is called the critical angle.
If θc is the critical angle, the refractive index (μ) is given by:
Calculation:
If θc is the critical angle, the refractive index (μ) is given by:
From Brewster’s law, the polarization angle,
When the ray incident at the polarization angle, the angle between the reflected and refracted rays are 90o.
So, the angle of refraction (r) + angle of reflection (ip) = 90°
⇒ r = 90° - 60° = 30°
Hence option 1 is correct.
The light has ____ nature.
Answer (Detailed Solution Below)
Polarisation Question 10 Detailed Solution
Download Solution PDFCONCEPT:
- Light: It is an electromagnetic wave.
- Light shows dual nature i.e. wave and particle.
Phenomenon explaining the wave nature of light is/are:
- Interference
- Diffraction
- Polarisation
Phenomenons explaining the particle nature of light are:
- Photoelectric effect
- Compton Scattering
- Photons associated with light shows that the energy is Quantised and occurs in discrete levels.
EXPLANATION:
- From the above discussion, the light has a dual nature. So option 4 is correct.
A 20 cm long tube containing 15% sugar solution rotates the plane of polarization of light by 21°. The specific rotation of sugar solution is:
Answer (Detailed Solution Below)
Polarisation Question 11 Detailed Solution
Download Solution PDFConcept:
A polarimeter consists of a light source, two polarizing prisms or filters, a liquid cell placed between the two polarizers, an eyepiece and a protractor for measuring the angular rotation of light by the solution.
Specific rotation α:
θ = measured rotation in angular degrees, c = concentration in grams per millilitre of solution, l = cell length in decimetres
Calculation:
20 cm = 2 decimetres
Calculate phase difference introduced by a calcite crystal plane of thickness 30 microns between ordinary and extraordinary light of wavelength 6000 Å. Given that μ0 = 1.554 and μe = 1.547
Answer (Detailed Solution Below)
Polarisation Question 12 Detailed Solution
Download Solution PDFConcept:
If μ0 and μe are refractive index of O-ray and E-ray respectively, λ is the wavelength of light and t is the thickness of retardation plate Then;
Path difference between O-ray and E-ray is given by,
Δ = t(μ0 - μe) ---(1)
And, phase difference between O-ray and E-ray is given as;
Calculation:
Given: t = 30 micron, μ0 = 1.554, μe = 1.547, λ = 6000 Å
From equation (1) ;
Path difference can be calculated as;
Δ = 30 × 10-6 × (1.554 – 1.547)
Δ = 30 × 0.007 × 10-6
Δ = 21 × 10-8 m
From equation (2) ;
δ = 0.7π
Important Point:
- Negative crystals are crystals in which refractive index of E-ray (μe) is less than that O-ray (μ0) ⋅ [μe 0]
- Positive crystals are crystals in which refractive index of Oray is less than that for E ray [μ0 e]
An unpolarised beam is incident at an angle 60° on a glass surface and after reflection it is linearly polarised. The approximate refractive index of the glass is:
Answer (Detailed Solution Below)
Polarisation Question 13 Detailed Solution
Download Solution PDFConcept:
- The angle of incidence at which a beam of unpolarized light falling on a transparent surface is reflected as a beam of completely plane polarised light is called polarising or Brewster angle. It is denoted by ip.
- Brewster's law: It states that when a ray is passed through some transparent medium having refractive index μ at any particular angle of incidence, the reflected ray is completely polarized; and the angle between reflected and refracted ray is 900.
μ = tan θB
Where,
μ = refractive index and
θB is Brewster's angle or polarizing angle (ip).
Calculation:
Given that:
The angle of incidence (ip) = 60°
Refractive index (μ) = tan θB = tan ip = tan 60° = √3 = 1.7
Hence option 3 is correct.
Nature of electromagnetic waves is transverse. Evidence of this is given by
Answer (Detailed Solution Below)
Polarisation Question 14 Detailed Solution
Download Solution PDF- Polarization: This is a process by which unpolarised light is transformed into polarized light.
- Polarisation tells about the wave nature of light, as the light wave is polarised in a particular plane.
- The longitudinal waves cannot be polarised.
EXPLANATION:
- Polarization does not work on the longitudinal wave.
- Only transverse waves can be polarized.
- So, by the phenomenon of polarization, electromagnetic waves show transverse nature. So the correct answer is option 2.
Additional Information
Diffraction |
|
- Electromagnetic waves: The wave which is generated due to vibration between electric field and magnetic field and it does not need any medium to travel is called an electromagnetic wave. It can travel through a vacuum.
- Light is a form of energy which is an example of electromagnetic waves.
- Electromagnetic waves are transverse in nature because they propagate by varying their electric and magnetic fields so that both the fields propagate perpendicular to each other.
Polarised light can be produced by:
Answer (Detailed Solution Below)
Polarisation Question 15 Detailed Solution
Download Solution PDFA light wave that has vibrations in more than one plane is known as unpolarized light.
- Polarized waves are light waves in which the vibrations occur in a single plane.
- A Nicol prism is made up of two prisms of calcite (CaCO3).
- Nicol prism is designed in such a way that it eliminates the ordinary rays by total internal reflection and only allow the extraordinary rays to transmit through it.
Notes:
- Nicol prism is used for producing a polarised beam of light from an un-polarised beam. Hence, option 2 is correct.
- It is based on the principle of action which involves refraction as it passes into the lower half of the prism.
- It leaves the prism as polarised light after undergoing another refraction as it exits the far right side of the prism. Thus its action is based on double refraction.