Optics Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. The bending of light when it passes from one medium to another is called

1. Reflection
2. Refraction
3. Total internal reflection
4. Diffraction

Ans. The correct answer is b. Refraction

Explanation: Refraction is the phenomenon that occurs when light bends as it passes from one medium to another.

Ques. Light has the properties of

1. Particle
2. Wave
3. Both wave and particle
4. Neither wave nor particle

Ans. The correct answer is c. Both wave and particle

Explanation: The hypothesis of light as a particle was largely abandoned until the end of the nineteenth century when Albert Einstein revived it. Now that light's dual nature as "both a particle and a wave" has been established, its fundamental theory has developed from electromagnetics into quantum mechanics.

Ques. Photons have a mass of more than two gms.

1. True
2. False

Ans. The correct answer is b. False

Explanation: The photon is a massless quantity that moves at the speed of light in a vacuum.

Ques. Dispersion can be observed through

1. Wall
2. Prism
3. Paper
4. Wood

Ans. The correct answer is b. Prism

Explanation: A prism is an optical instrument that allows us to see how white light disperses into its constituent colors.

Ques. Which among the following is the property of light?

1. Total internal reflection
2. Reflection
3. Diffraction
4. All of the above

Ans. The correct answer is d. All of the above

Explanation: Light can undergo reflection, refraction, total internal reflection, and diffraction.

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Short Answers Questions [2 Marks Questions]

Ques. What is optics?

Ans. Optics is the branch of physics concerned with the behavior and characteristics of light as it interacts with matter. Optics also studies the devices used to observe light's behavior.

Ques. Define total internal reflection.

Ans. Total internal reflection is the phenomenon in which waves arriving at the interface from one medium to another are entirely reflected back into the first medium rather than refracted into the second medium.

Ques. What is a prism?

Ans. A prism is a refracting material that is homogeneous, solid, and transparent and is surrounded by two flat surfaces that are inclined at an angle. The most often used prism has two parallel triangle sides and three rectangular surfaces. They are constructed of glass or another transparent material that has been precisely cut.

Ques. What is an optical instrument?

Ans. An optical instrument is a device that processes light waves, either to improve the quality of images or to analyze and identify their characteristics. Periscopes, microscopes, telescopes, and cameras are common examples.

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Long Answers Questions [3 Marks Questions]

Ques. What are the properties of an image formed by a plane mirror?

Ans. The following are the properties of the image formed by a plane mirror are

• The image formed by the plane mirror is of the same size as that of the object.
• The image formed by the plane mirror is at the same distance behind the mirror as the object in front of it.
• The image formed by a plane mirror is virtual.
• The image formed by a plane mirror is erect
• The image formed by a plane mirror is laterally inverted.
• The minimum length of the plane mirror required to have the full-length image of a person standing in front of it is equal to half of the height of the person.

Ques. What is the classification of optics in physics?

Ans. Optics is generally classified into two categories

• Geometrical optics: Geometrical optics, often known as ray optics, is an optics model that defines light propagation in terms of rays. In geometrical optics, a ray is a useful abstraction for estimating the paths along which light propagates under particular conditions. Certain optical phenomena, such as diffraction and interference, are not taken into consideration by geometrical optics.
• Physical optics: Physical optics, often known as wave optics, is the discipline of optics that examines interference, diffraction, polarisation, and other phenomena for which the geometric optics ray approximation is not applicable. This usage excludes factors such as quantum noise in optical communication, which is researched under the coherence theory sub-branch.

Ques. What are the assumptions of geometrical optics?

Ans. The following are the assumptions of geometrical optics

• Light rays can move in straight lines in a homogenous medium.
• Light rays can bend and, in certain cases, divide in two at the interface of two different media.
• In a medium with a changing refractive index, light rays can take curved pathways.
• Rays of light can be absorbed or reflected.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the properties of light?

Ans. The following are the properties of light

• Light is a form of energy that induces the sensation of sight in our eyes.
• It is the visible part of the electromagnetic spectrum of wavelength ranging from 400 nm to 780 nm.
• Light travels in a straight line in a vacuum with a speed of 3 x 108 m/s.
• Since the size of the objects that we see in our daily lives is very large as compared to the wavelength of the light, it appears to be traveled in a straight line.
• Light can show the phenomenon of reflection. It is the phenomenon in which light travels through one medium, impacting the surface of another, and returns to the original medium.
• Light can show the phenomenon of refraction. It is a phenomenon in which the speed of light changes as it passes from one medium to another and the ray of light bends.
• Light can also show the phenomenon of dispersion, interference, diffraction, and polarization.

Ques. What are the applications of optics?

Ans. The following are the applications of optics

• The phenomenon of refraction is used in the case of convex and concave lenses to generate an image of an object.
• Geometrical optics is the study of light as described by rays. It is used to investigate how images form in an optical system.
• It is employed in the visual diagnosis of human body defects and mysteries in medical applications.
• Optics is also employed in human tissue therapeutic procedures.
• The use of eyeglasses and contact lenses for solving various visual problems.
• Telescopes are used for exploring distant universes.
• Microorganisms are discovered using microscopes.
• Data transmission, storage, retrieval, surgery, and weapon aiming all make use of lenses, mirrors, lasers, and optical fibers.

Ques. Explain the following, giving reasons :

1. When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency.
2. When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a reduction in the energy carried by the wave?
3. In the wave picture of light, the intensity of light is determined by the square of the amplitude of the wave. What determines the intensity in the photon picture of light?

Ans. The reasons for the statements mentioned above are

1. Reflection and refraction occur as a result of incident light interacting with atomic components of matter that vibrate at the same frequency as the incident light. As a result, the frequency of reflected and refracted light is the same as the frequency of incident light.
2. No, light's energy will not decrease. This is because the energy transported by a wave is determined by its amplitude rather than its speed of propagation.
3. The number of photons incident usually on passing a unit area per unit of time determines the intensity of light in the photon picture at a certain frequency.

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