Optics MCQs

Ans 1. (a) reflection of light

Explanation: When the light strikes with the border between two different media, reflection occurs, which is defined as an abrupt change in the direction of propagation of the wave.

Ans 2. (b) Angular dispersion

Explanation: Angular dispersion refers to the variation in a deviation between any two shades. In terms of angular dispersion, the formula is: δV-δR=(μV-μR)A

where μV and μR stand for the corresponding refractive indices of violet and red light.

 δ = (δV + δR / 2) is the measure of mean deviation.

Ans 3. (d) 1°

Explanation: The necessary formula is δ = (μ-1)A

By joining two prisms, then

δ=δ+δ’=(μ-1)A+(μ’-1)A’=0

So, A’=-(μ−1)Aμ‘−1

A’=-(1.15−1)1.45−1 × 3

A’=-1o

As a result, the other prism has an angle of 1° and faces away from the first prism.

Ans 4. Chromatic aberration

Explanation: Chromatic aberration is the name given to this problem. It happens because the optics' refractive indices for various light wave lengths vary. Because every colour in the optical spectrum cannot be concentrated at a common shared spot, chromatic aberration expresses itself as "fringes" of colour along borders that separate high contrast areas of the image.

Ans 5. (a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion.

Explanation: As light is reflected by a convex mirror, it is bent to a greater or lesser extent depending on how far away a point is from the centre. A convex mirror produces a smaller picture than a plane (flat) mirror does, as a result. A convex mirror has a greater field of view than a plane mirror since more images may fit onto the mirror due to the smaller size of the image. When a wide-angle mirror is required to see traffic, they are employed.

Ans 6. (a) True

Explanation: An object's characteristic is its refractive index. Different colours turn via different angles as they pass through the prism because δ=(μ-1)A. Dispersion is brought on by this. As a result, a prism's object's refractive index varies depending on the colour.

Ans 7. (a) Black

Explanation: It will seem black to an astronaut. Because there is an atmosphere here on earth, we can see a blue sky. The colour of the sky is revealed by the way the atmosphere reflects back light from the sun. Since there is no atmosphere in space, light beams do not refract as they travel to the astronomer's eyes, giving the impression that everything is black.

Ans 8. (b) Decrease 

Explanation: Dispersion gradually decreases. When light hits a glass prism from the air, it has already begun to disperse somewhat, but less so than when it first enters a glass prism first from air.

Ans 9. (b) False

Explanation: This claim is not true at all. Color wavelength and material's refractive index are inversely proportional to one another. For instance, because red has the longest wavelength, it will also have the lowest refractive index. Violet has the highest refractive index and the shortest wavelength of all the colours.

Ans 10. (b) Have high resolution

Explanation: Because the objective lens' aperture is larger than the eyepiece's, it can collect more light from a distant object and produce a brilliant picture of that thing. So, it is safe to state that an astronomical telescope has a large aperture to provide great resolution of a distant object.

Ans 11. (a) violet innermost, red outermost

Explanation: In a primary rainbow, violet is on the innermost arc and red is on the outermost arc. When viewed through the eyes, a water droplet that is 42° across appears to be emitting red light, whereas a droplet that is 40° across appears to be emitting violet light.

Ans 12. (c) It needs a material medium to propagate.

Explanation: Light waves can travel through space without the aid of a physical medium. Additionally, they move through vacuum. Light involves the movement of energy, as demonstrated by the heating of a metallic plate placed in the path of light beams. Also, the constant speed of light is 3 × 108 m/s.

Ans 13. (c) both (a) and (b)

Explanation: Both the refractive index of water and oil are higher than the refractive index of a lens when placed in air. As a result, the lens will behave as a concave lens in that liquid even though it was convex (focal length positive) in air. Thus, in both oil and water, convex lenses become less convergent.

Ans 14. (a) Violet

Explanation: Violet light will have the greatest variation because it has the lowest wavelength.

Ans 15. (a) Frequency

Explanation: Frequency is the only aspect of light that remains constant as it moves from one medium to another. When light travels from one medium to another, its other qualities, such as wavelength and speed, change.

Ans 16. (c) Angle of deviation

Explanation: A prism is a two-surfaced enclosure that is homogeneous, transparent, and inclined at an angle. The angle between the incident and emerging rays is referred to as the angle of deviation, and these surfaces are referred to as the refracting surfaces.

Ans 17. (c) Almost form a point image of a point source.

Explanation: In a spherical mirror, the rays that are reflected from a point source do not converge at one spot. It is avoided by taking paraxial (near the major axis) rays. It almost creates a point source's picture.

Ans 18. (d) Refraction

Explanation: It is air refraction that causes the sun's disc to appear flatter during sunrise and dusk. The atmosphere's density and refractive index decrease with height, causing a variation in the amount of refraction of the sun's rays above and below the horizon.

Ans 19. (a) Cylindrical lens

Explanation: Using a spherical cylindrical lens will fix the astigmatism eye problem. Astigmatism can alter how light travels through the eye, resulting in distorted and fuzzy vision.

Ans 20. (b) 400 nm to 750 nm

Explanation: There are several different types of electromagnetic (EM) radiation that we encounter every day, including radio waves, microwaves, X-rays, and gamma rays. Although visible light only makes up a small percentage of the electromagnetic spectrum, which encompasses a wide range of electromagnetic wavelengths, sunlight is also a kind of EM energy.