Chapter 16 Light mcqs & important questions science | class 8th

MCQ Questions for Class 8 Science: Ch 16 Light

1. Beam of light striking the reflecting surface is called

(a) reflecting ray

(b) incident ray

(c) refracted ray

(d) normal ray

► (b) incident ray

2. What makes objects visible?

(a) The absorption of light by objects

(b) The reflected light from the object

(c) The total internal reflection taking place in an object

(d) The refracted light from the object

► (b) The reflected light from the object

3. If the angle of incidence is 50°, then calculate the angle between the incident ray and the reflected ray.

(a) 50°

(b) 100°

(c) 130°

(d) 80°

► (b) 100°

4. _________ refers to collection of rays.

(a) Photon

(b) Beam

(c) Shadow

(d) Image

► (b) Beam

5. Which of the following travels faster?

(a) Jet Aero plane

(b) Sound

(c) Light

(d) Supersonic plane

► (c) Light

6. What makes the object visible?

(a) Size

(b) Time

(c) Colour

(d) Light

► (d) Light

7. An example of luminous object is

(a) Star

(b) Smooth surface

(c) Mirror

(d) Cloth

► (a) Star

8. With what is glass coated in order to convert it into a mirror?

(a) Silver

(b) Copper

(c) Aluminium

(d) Platinum

► (a) Silver

9. In a periscope, how are the reflecting mirrors arranged?

(a) Perpendicular to each other

(b) Parallel to each other

(c) At an angle of 90°

(d) At an angle of 60°

10. How many images are obtained when plane mirrors are arranged parallel to each other?

(a) A single image

(b) Two images

(c) Infinite number of images

(d) Zero image

► (c) Infinite number of images

11. Angle of incidence is always

(a) Equal to angle of reflection

(b) Equal to angle of refraction

(c) More than angle of reflection

(d) Less than angle of reflection

► (a) Equal to angle of reflection

12. Which of the following is used by E.N.T. doctors?

(a) Convex mirror

(b) Convex lens

(c) Plane mirror

(d) Concave mirror

► (d) Concave mirror

13. What is the phenomenon of light bouncing back into the same medium called?

(a) Reflection

(b) Refraction

(c) Dispersion

(d) Splitting

► (a) Reflection

14. What is the nature of image formed on the retina of human eye of an object?

(a) Virtual and erect

(b) Virtual and inverted

(c) Real and erect

(d) Real and inverted

► (d) Real and inverted

15. Convex lens focus a real, point sized image at focus, the object is placed         

(a) At focus

(b) Between F and 2F

(c) At infinity

(d) At 2F

► (c) At infinity         

16. Braille system is used by

(a) Hearing impaired

(b) Black people

(c) Blind people

(d) African people

► (c) Blind people

17. Speed of light is fastest in

(a) Air

(b) Water

(c) Diamond

(d) Glass

► (a) Air

18. Splitting of white rays of light into seven colours is called

(a) Dispersion of light

(b) Reflection of light

(c) Refraction of light

(d) Scattering of light

► (a) Dispersion of light

19. A number of rays from different direction assemble at point are called

(a) Intersecting rays

(b) Parallel rays

(c) Divergent rays

(d) Convergent rays

► (d) Convergent rays

20. What is the name of object through which light can pass?

(a) Opaque

(b) Translucent

(c) Transparent

(d) Luminous

► (c) Transparent

21. The image formed by plane mirror is

(a) real and inverted

(b) real and erect

(c) virtual and inverted

(d) virtual and erect

► (d) virtual and erect

22. The process of banding of seven colours is called

(a) dispersion

(b) spectrum

(c) reflection

(d) normal

► (a) dispersion

23. From a source light travels as rays which are

(a) Divergent

(b) Convergent

(c) Parallel

(d) Diffused

► (c) Parallel

24. What happens in lateral inversion?

(a) The right side of the object will be on the right side of the image.

(b) The left side of the object will be on the left side of the image.

(c) The top of the object will be the bottom of the object.

(d) The right side of the object will be on the left side of the image.

► (d) The right side of the object will be on the left side of the image.

25. The angle of reflection is equal to the angle of incidence

(a) Sometimes

(b) Always

(c) Never

(d) Under special case

► (b) Always

Class 8 Science Chapter 16 Extra Questions and Answers Light

Extra Questions for Class 8 Science Chapter 16 Light with Answers Solutions

Light Class 8 Extra Questions Very Short Answer Type

Question 1.
Why fingers appear blurred when we move our hand very fast in front of our eyes?
Answer:
This is due to persistence of vision 1/16th of a second.

Question 2.
What makes things visible?
Answer:
When light reaches our eyes after striking an object, we are able to see an object.

Question 3.
Which element is used at the back of plane mirror?
Answer:
Silver

Question 4.
The distance between the object and its image formed by a plane mirror appears to be 18 cm. What is the distance between mirror and the object?
Answer:
9 cm

Question 5.
How is hypermetropia corrected?
Answer:
It is corrected by using convex lens.

Question 6.
How is myopia corrected?
Answer:
It is corrected by using concave lens.

Question 7.
A ray of light is incident on a mirror at an angle of 40°. What is the angle of reflection ?
Answer:
40°

Question 8.
Name a device which works on the principle of multiple reflection.
Answer:
Periscope

Question 9.
Can we see an object in the dark?
Answer:
No

Question 10.
What is the nature of the image formed by the plane mirror?
Answer:
Virtual and erect

Question 11.
Where is the image formed in a plane mirror?
Answer:
Behind the mirror

Question 12.
The angle between the incident ray and reflected ray is 100°. What is the value of angle of incidence?
Answer:

Question 13.
What is yellow spot?
Answer:
It is highly light sensitive spot for seeing things with highest clearness.

Question 14.
Give an example of night bird.
Answer:
Owl

Question 15.
What do we call the image that cannot be obtained on a screen?
Answer:
Virtual

Question 16.
Show mathematically, the first law of reflection.
Answer:
∠i = ∠r

Question 17.
Name the phenomenon shown in the figure.
Answer:
Lateral inversion.

Question 18.
Express the mathematical formula to calculate the number of images formed when two mirrors are inclined at θ angle. 360°
Answer:
Number of images

Question 19.
How many colours are there in a spectrum of white light?
Answer:
Seven

Question 20.
Name the scientist who studied that if a white light is passed through a prism, it splits into different colours.
Answer:
Sir Issac Newton

Question 21.
Name the spot inside the human eye where the image is not visible.
Answer:
Blind spot

Question 22.
Name the liquid found between the cornea and lens.
Answer:
Aqueous humour

Question 23.
Name the liquid found between the lens and the retina.
Answer:
Vitreous humour

Question 24.
Define the incident ray.
Answer:
The ray of light striking the surface is called an incident ray.

Question 25.
Define angle of reflection.
Answer:
The angle between the reflected ray and the normal is called the angle of reflection.

Light Class 8 Extra Questions Short Answer Type

Question 1.
Define light.
Answer:
Light is defined as a form of energy that stimulates sight and makes things visible.

Question 2.
What is reflection?
Answer:
The bouncing back of light into the same medium after it falls on a surface is called reflection.

Question 3.
What is a mirror?
Answer:
A piece of glass with a shiny metal-covered at back, that reflects light, producing an image of the object in front of it is known as mirror.

Question 4.
State the two laws of reflection.
Answer:
The two laws of reflection are:

• The angle of incidence is always equal to the angle of reflection.
• The incident ray, the reflected ray and normal all lie in the same plane.

Question 5.
How do we see various objects?
Answer:
We see various objects due to reflection. As we know all surface reflect light, when light falls on any object, it reflects the light. The reflected light reaches our eyes and we are able to see the object.

Question 6.
What do you mean by reflected ray?
Answer:
The ray of light which is returned back into the same medium after the incident ray strikes the surface ’ is called reflected ray.

Question 7.
What is irregular reflection?
Answer:
Irregular reflection is defined as the reflection of light from an uneven surface. In irregular reflection, the reflected beam is not parallel.

Question 8.
List the characteristics of an image formed in a plane mirror.
Answer:
The characteristics of an image formed in a plane mirror are:

• It is virtual.
• It is erect.
• It is of same size as the object.

Question 9.
What is lateral inversion?
Answer:
The phenomenon of changing left side to right and right side to left by the mirror while forming image is called lateral inversion.

Question 10.
What is the far point and near point of the human eye with normal vision?
Answer:
In optics, the farthest and closest point at which an object can be brought into focus by the eye are called far point and near point of the eye respectively. The far point of the human eye with normal vision is infinity. The near point of the human eye with normal vision is 25 cm.

Question 11.
What is aqueous humour?
Answer:
The space between the cornea and lens is filled with a liquid called the aqueous humour.

Question 12.
Differentiate between rod and cone cells.
Answer:
Rods are the rod-shaped cells present in the retina of an eye which are sensitive to dim light whereas cones are the cone-shaped cells present in the retina of the eye which are sensitive to bright light.

Light Class 8 Extra Questions Long Answer Type

Question 1.
Write a short note on Braille system.
Answer:
The most popular resource for visually challenged persons is Braille. Braille system was developed by Louis Braille. He himself was a visually challenged person. There is Braille code for common languages, mathematics and scientific notation. Many Indian languages can be read using the Braille system.

Braille system has 63 dot patterns or characters. Each character represents a letter, a combination of letters, a common word or a grammatical sign. Dots are arranged in cells of two vertical rows of three dots each. Patterns of dots to represent some English letters and some common words are shown in Fig. 16.26.

These patterns when embossed on Braille sheets help visually challenged persons to recognise words by touching. To make them easier to touch, the dots are raised slightly. Visually challenged people learn the Braille system by beginning with letters, then special characters and letter combinations. Methods depend upon recognition by touching. Each character has to be memorised. Braille texts can be produced by hand or by machine. Typewriter-like devices and printing machines have now been developed.

Question 2.
Explain the phenomenon of dispersion of light.
Answer:
Dispersion is defined as the phenomenon of splitting of white light into different colours on passing through a transparent medium such as prism. When white light is passed through a prism, it splits into seven colours. It is observed that the colours are in the following order:
Violet (V), Indigo (I), Blue (B), Green (G), Yellow (Y), Orange (O) and Red (R). The order of colours can be remembered by the acronym VIBGYOR. This coloured band is called spectrum of white light.

Question 3.
Write a note on ‘The Human Eye’
Answer:
Eye is a sense organ that enables us to see the world around us. It is roughly spherical in shape

• The first part that is bulged outward is called ‘cornea. It protects the eye.
• Behind the cornea, the coloured part of the eye, iris is present. It controls the size of the pupil.
• Pupil is a small opening in the cornea which allows the light to enter the eye.
• Behind the iris, eye lens is present which is a convex lens. It focus the image on retina, by bending the light rays.
• Retina is the inner back surface of the eye which acts as a screen to form image. It is sensitive to light.
• The sensation of the image formed on the retina is carried to the brain by the optic nerve.
• Optic nerve is connection between the eye and the

Question 4.
Write the ways to protect your eyes.
Answer:
Eyes are very delicate organ that enable us to see this colourful world. Thus, we must protect our eyes and take proper care of them.
Following are the ways to protect the eye:

• Always sit straight while reading or writing.
• Never read while walking or lying down.
• Wash your eyes frequently with clean water.
• Never read in the dim or too much bright light.
• Never rub your eyes with hands.
• Never bring the book too close to your eyes.
• Eat foods rich in vitamin A.

Question 5.
Explain some common eye defects in human.
Answer:
Some eye diseases are:
(i) Cataract: A cataract is a clouding of the lens in the eye leading to a decrease in vision. It can affect one or both eyes. Often it develops slowly. Symptoms may include faded colours, blurry vision, halos around light, trouble with bright lights, and trouble seeing at night. This may result in trouble driving, reading, or recognising faces. Cataracts are the cause of half of blindness and 33% of visual impairment worldwide. Cataract is treated by replacing the opaque lens with a new artificial lens.

(ii) Myopia: Near-sightedness or myopia, is the most common refractive error of the eye. Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. It can be corrected using spectacles made of concave lens.

(iii) Hypermetropia: Hypermetropia or long-sightedness occurs when eyeball is too short or the cornea or crystalline lens does not refract the light enough. This lead to formation of the image of a nearby object behind the retina. A hypermetropic person may have blurred vision when looking at objects close to them, and clearer vision when looking at objects in the distance. By placing a convex (plus powered) lens in front of a hypermetropic eye, the image is moved forward and focuses correctly on the retina.

(iv) Astigmatism: It is a defect in the eye or in a lens caused by a deviation from spherical curvature, which results in distorted images, as light rays are prevented from meeting at a common focus. It can be corrected by using a convex lens or concave lens or both.