To Determine the Refractive Index of a Glass Slab Using a Travelling Microscope Viva Questions

The refractive index (or refraction index) of an optical media is a dimensionless quantity that indicates the ability of the medium to bend light. 

• The refractive index describes how much light is bent, or refracted, as it enters a material.
• The refractive indices also determine how much light is reflected at the interface, as well as the critical angle for total internal reflection, intensity (Fresnel's equations), and Brewster's angle.
• The refractive index can change depending on the wavelength that causes dispersion of light i.e. when white light is refracted, it splits into component colours.

The formula to calculate the refractive index of a medium is given by

n = c/v

Where

• n is the refraction index of the medium
• c is the speed of light in air or vacuum
• v is the speed of light in the medium. 

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Ques. What is a microscope?

Ans. A microscope is a device that magnifies the image of a small object, exposing details that the unaided eye cannot perceive. The optical microscope, which uses visible light focused through lenses, is the most common type of microscope.

Ques. What is a traveling microscope?

Ans. A traveling microscope is an optical instrument for measuring length with a resolution of 0.01mm. The device consists of a microscope placed on two rails that are either fixed to or part of an extremely rigid bed. The microscope's position can be changed coarsely by sliding along the rails, or finely by twisting a screw.

Ques. What is the field of view in a microscope?

Ans. The diameter of the illuminated circle viewed through the eyepiece of a microscope is known as its field of view. With increasing magnification, the field of view decreases.

Ques. What is the depth of focus in a microscope?

Ans. The depth of focus of a microscope is defined as the distance between the objective lens and the model plane. The depth of focus varies from person to person and is also affected by the quality of focus.

Ques. What is the depth of field in a microscope?

Ans. In a microscope, the depth of field is defined as the distance between the farthest plane in focus and the nearest object plane in the same focus. Because the depth of field in a microscope is so small, it is measured in microns.

Ques. Is the speed of light faster in glass or water?

Ans. The speed of light in water is faster than in glass because the refractive index of glass is 1.5 and the refractive index of water is 1.3. We know that the refractive index of a medium and the velocity of light in that medium are inversely related to each other using the equation n = c/v. As a result, light travels faster in water.

Ques. What is a refractive index?

Ans. When a light beam bends as it travels from one medium to another, the measurement of that bending is known as the refractive index. It can be written as n = c/v.

Ques. Will there be any change in the wavelength of the red light when it enters glass from the air?

Ans. The relation between the wavelength of light in air (λ) and the wavelength of light in medium (λ_m) is given by

λ_m = λ/n

Where n is the refraction index of the medium.

Since the refractive index of the glass is 1.5, therefore wavelength of red light in the glass is 1/1.5 times the wavelength of red light in air. Hence the wavelength of red light decreases.

Ques. What is the law of refraction?

Ans. According to the law of refraction

• The incident ray, the refracted ray, and the normal to the interface at the point of incidence lie in the same plane.
• The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for any two given media.

Ques. What is the absolute refractive index?

Ans. Absolute refractive index (n) is defined as the ratio of the speed of light in vacuum or air (c) to the speed of light in the medium(v).

Ques. What is the formula to calculate the refractive index of a medium?

Ans. The formula to calculate the refractive index of a medium is given by

n = c/v

Where

• n is the refraction index of the medium
• c is the speed of light in air or vacuum
• v is the speed of light in the medium.

Ques. What is the apparent shift?

Ans. The apparent shift is defined as the difference in distance between the object and the image from the refracting surface.

Ques. On what factors does apparent depth depend?

Ans. Apparent depth depends on

• Nature of the medium
• The thickness of the medium
• Color of the light

Ques. What is the normal shift?

Ans. When an object is put in one medium and viewed along the normal from another medium, there is an apparent shift in its location, which is known as the normal shift.

Ques. What is the SI unit of normal shift?

Ans. The SI unit of normal shift is a meter.

Ques. What are the sources of error in the experiment – To determine the refractive index of a glass slab using a traveling microscope.

Ans. The sources of error in the experiment are

• The coating of lycopodium powder on the glass slab might be thick.
• The microscope's scale may not be correctly calibrated.

Ques. Why does a slab not deviate and distribute light like a prism?

Ans. A slab's refracting faces are parallel. The emerging ray moves in the same direction as the incident beam. There is no dispersion in this case.

A prism's refracting faces are not parallel. The emerging ray does not follow the incident beam's path. As a result of the departure, there is dispersion.

Ques. What is the minimum number of readings required in the experiment -To determine the refractive index of a glass slab using a traveling microscope?

Ans. There are three readings are required

• Reading one ⇒ without slab
• Reading two ⇒ with slab
• Reading three ⇒ with sawdust

Ques. What is the use of a traveling microscope during the experiment?

Ans. The use of the traveling microscope during the experiment is to measure the refractive index of the glass slab.

Ques. What is the significance of lycopodium powder in this experiment?

Ans. The presence of lycopodium powder ensures that the microscope's focus is not on the bottom surface of the transparent slab.

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