Light – Short Answer Type Questions
CBSE Class 8 Science – Chapter 16: Light (Short Answer Questions)
These Short Answer Questions are designed strictly as per the NCERT Class 8 Science textbook,
making them ideal for CBSE Class 8 Board Examination style preparation and quick revision.
CBSE Board Examinations – Topic-wise Short Answer Questions with Answers
Below is a comprehensive, topic-wise set of 50 Short Answer Type Questions from
Chapter 16: Light. Answers are written in clear, student-friendly language to help
Class 8 learners revise concepts thoroughly and perform well in CBSE examinations.
Topic 1
Basic Ideas of Light, Visibility and Shadows
Q1. What is light and why is it important for us?
Ans. Light is a form of energy that enables us to see objects. It is important because
without light, even objects around us cannot be seen and our surroundings would appear completely dark.
Q2. Distinguish between luminous and non-luminous objects with one example each.
Ans. Luminous objects emit their own light, e.g. the Sun or a glowing bulb.
Non-luminous objects do not emit light, they only reflect it, e.g. a chair or a book.
Q3. Why can we not see objects in a room when all lights are switched off?
Ans. We see an object only when light from it enters our eyes. In a dark room there is no light to
reflect from the objects into our eyes, so the objects are not visible.
Q4. Define rectilinear propagation of light. Give one simple example to show it.
Ans. The property of light by which it travels in a straight line is called
rectilinear propagation. The formation of sharp shadows of objects kept in sunlight
is a simple example showing that light travels in straight lines.
Q5. What is a shadow? State the conditions necessary for its formation.
Ans. A shadow is a dark region formed on a screen when an opaque object blocks the path of light.
For a shadow to form, we need a source of light, an opaque object and a screen behind the object.
Q6. How are opaque, transparent and translucent objects different in terms of light transmission?
Ans. Opaque objects do not allow light to pass through them at all.
Transparent objects allow light to pass completely, so we can see clearly through them.
Translucent objects allow light to pass partially, so objects behind them appear blurred.
Q7. Why does the shadow of a tree appear longer in the early morning and late evening?
Ans. In early morning and late evening, the Sun is low in the sky, so the light rays fall obliquely on objects.
Oblique rays produce longer shadows as compared to the shadows at noon when the Sun is almost overhead.
Q8. A transparent glass does not cast a sharp shadow. Explain why.
Ans. Transparent glass allows most of the light to pass through it, so only very little light is blocked.
Because light is hardly obstructed, a dark and sharp shadow is not formed, only a faint outline may be seen.
Topic 2
Reflection of Light – Terms and Laws
Q9. What is meant by reflection of light?
Ans. When a beam of light falls on a surface and bounces back into the same medium instead of passing through it,
the phenomenon is called reflection of light.
Q10. Define incident ray, reflected ray and normal at the point of incidence.
Ans. The incident ray is the ray of light that strikes a surface.
The reflected ray is the ray that bounces back from the surface.
The normal is an imaginary line drawn perpendicular to the surface at the point where the incident ray strikes.
Q11. What is angle of incidence and angle of reflection?
Ans. The angle of incidence is the angle between the incident ray and the normal.
The angle of reflection is the angle between the reflected ray and the normal at the point of incidence.
Q12. State the two laws of reflection of light.
Ans. (i) The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
(ii) The angle of reflection is always equal to the angle of incidence (∠r = ∠i).
Q13. How can you verify experimentally that angle of incidence is equal to angle of reflection?
Ans. Draw a line representing a mirror, mark a normal and an incident ray at a known angle using a ray box.
Trace the reflected ray and measure ∠i and ∠r with a protractor. Repeating with different angles shows that ∠i = ∠r each time.
Q14. Why is the normal drawn at the point of incidence while studying reflection?
Ans. Angles of incidence and reflection are measured from the normal, not from the surface.
Drawing the normal helps us define these angles accurately and apply the laws of reflection correctly.
Q15. Does reflection of light take place only from smooth surfaces? Explain.
Ans. No. Reflection takes place from both smooth and rough surfaces.
However, smooth surfaces give regular reflection with clear images, while rough surfaces cause diffused reflection with scattered rays and no clear image.
Q16. What is meant by regular reflection? Give one example.
Ans. When parallel rays of light strike a smooth surface and reflect in a definite, parallel direction,
it is called regular reflection. Reflection from a plane mirror or calm water surface is an example.
Q17. What is diffused reflection? Why does it occur?
Ans. When light falls on a rough surface and is scattered in many directions, it is called
diffused reflection. It occurs because each tiny part of the uneven surface reflects light in a different direction.
Q18. Do the laws of reflection hold for diffused reflection also? Give reason.
Ans. Yes, the laws of reflection are obeyed at every point of a rough surface.
Only the direction of each reflected ray changes due to unevenness, causing scattering, but ∠i = ∠r at each small point.
Topic 3
Image Formation by Plane Mirror – Properties and Uses
Q19. Describe the nature (type) of image formed by a plane mirror.
Ans. A plane mirror forms a virtual, erect image which cannot be obtained on a screen.
The image appears to be behind the mirror, not in front of it.
Q20. How does the size of the image formed by a plane mirror compare with the size of the object?
Ans. The image formed by a plane mirror is of the same size as the object.
The mirror neither magnifies nor reduces the size of the image for a given object distance.
Q21. What is meant by lateral inversion? Give one example from daily life.
Ans. Lateral inversion is the left-right reversal of an image in a plane mirror.
The word “AMBULANCE” is written in reverse on the front of an ambulance so that drivers see it correctly in their rear-view mirrors.
Q22. A person is standing 1.5 m in front of a plane mirror. Where will his image appear?
Ans. In a plane mirror, the image is formed as far behind the mirror as the object is in front.
So, the image will appear 1.5 m behind the mirror along the same perpendicular line.
Q23. Why can’t the image formed by a plane mirror be obtained on a screen?
Ans. The image of a plane mirror is virtual.
The reflected rays only appear to meet behind the mirror; they do not actually converge there.
Since real rays do not meet, the image cannot be caught on a screen.
Q24. State any two uses of plane mirrors in daily life.
Ans. (i) Plane mirrors are used as dressing mirrors at home.
(ii) They are used in shops, salons and vehicle side mirrors for viewing oneself or surroundings clearly.
Q25. Why do we usually polish the back surface of the glass to make a mirror?
Ans. A reflecting coating like silver or aluminium is applied to the back surface of a glass sheet.
Glass protects the polished layer from damage and corrosion, ensuring a clear and durable reflecting surface.
Q26. Explain why we can see ourselves in a shiny steel plate but not in a rough wall.
Ans. A shiny steel plate acts almost like a mirror and gives regular reflection, forming a clear image.
A rough wall causes diffused reflection; the scattered rays do not form a sharp image, so we cannot see ourselves in it.
Topic 4
Multiple Reflection, Kaleidoscope and Periscope
Q27. What is multiple reflection of light? Give one situation where it occurs.
Ans. When light is reflected successively from two or more mirrors, it is called
multiple reflection. It occurs when an object is placed between two plane mirrors facing each other,
producing several images.
Q28. How does the angle between two mirrors affect the number of images formed?
Ans. When the angle between two mirrors decreases, the number of images formed increases.
If the mirrors are brought very close to facing each other, many images can be seen due to repeated reflections.
Q29. Name the device that uses multiple reflections to produce beautiful patterns. What is it used for?
Ans. A kaleidoscope uses multiple reflections to produce colourful, symmetrical patterns.
It is used by designers to get ideas for patterns on wallpapers, fabrics and decorative items.
Q30. Describe the basic construction of a simple kaleidoscope.
Ans. A simple kaleidoscope consists of three plane mirrors joined to form a triangular tube, with coloured glass pieces at one end.
The other end has a small hole to look through. Multiple reflections between mirrors create various patterns of these pieces.
Q31. What is a periscope? Mention one use.
Ans. A periscope is an instrument that uses mirrors to allow us to see objects that are not in direct line of sight.
It is used in submarines to see objects above the water surface while remaining hidden.
Q32. How many mirrors are used in a simple periscope and at what angle are they placed?
Ans. A simple periscope uses two plane mirrors. Each mirror is placed at an angle of 45° to the horizontal so that light is reflected twice and reaches the eye.
Q33. Explain briefly how a periscope helps a soldier in a trench.
Ans. The soldier holds the periscope above the trench. Light from objects ahead falls on the upper mirror,
reflects to the lower mirror and then to the eyes. In this way, the soldier can see outside without exposing his head and body.
Q34. Why are the inside walls of a kaleidoscope kept dark?
Ans. The inner walls are kept dark or black so that they do not reflect extra light.
This ensures that only light coming from the coloured glass pieces and mirrors forms bright, clear patterns.
Q35. Give one advantage and one disadvantage of using multiple reflections in devices.
Ans. Advantage: Multiple reflections help in seeing objects from hidden positions or producing beautiful patterns.
Disadvantage: Repeated reflections can reduce the brightness of light, making the images dimmer.
Q36. Why do we see an endless row of lights in some decoration arrangements with mirrors?
Ans. When lights are placed between two mirrors, light reflects back and forth many times between them.
This multiple reflection creates the impression of an endless row of lights, even though only a few bulbs are present.
Topic 5
Sunlight, Colours, Spectrum and Rainbow
Q37. Is sunlight white or coloured? How can we prove it?
Ans. Sunlight appears white but is actually made of many colours.
Passing sunlight through a glass prism splits it into a band of seven colours, proving that white light is a mixture of colours.
Q38. What is dispersion of light?
Ans. The phenomenon in which white light splits into its component colours on passing through a prism is called
dispersion of light.
Q39. Name the seven colours of the spectrum in correct order.
Ans. The seven colours in order are: Violet, Indigo, Blue, Green, Yellow, Orange and Red.
This order is remembered by the word VIBGYOR.
Q40. What is a spectrum?
Ans. The band of different colours obtained when white light is dispersed is called a
spectrum. Each colour in the spectrum corresponds to light of a particular wavelength.
Q41. Explain briefly how a rainbow is formed in the sky.
Ans. A rainbow forms when sunlight passes through tiny water droplets in the atmosphere after rain.
The droplets act like small prisms and cause dispersion and reflection of light, producing a coloured arc in the sky.
Q42. Why is the rainbow always seen in the direction opposite to the Sun?
Ans. For a rainbow to be visible, sunlight must enter the water droplets, disperse and then reach our eyes.
The observer faces the droplets with the Sun behind him, so the rainbow appears in the part of the sky opposite to the Sun.
Q43. What do we observe when a beam of white light passes through a glass prism?
Ans. We observe that the white light splits into a band of seven colours on the other side of the prism.
This band of colours is the spectrum, showing that white light is composed of many colours.
Q44. Why does a glass prism produce a spectrum but a glass slab does not?
Ans. A prism has two non-parallel surfaces, so the different colours bend (refract) through different angles and spread out to form a spectrum.
In a rectangular glass slab, opposite faces are parallel, so the colours recombine and we do not see a separated spectrum.
Topic 6
Human Eye, Eye Care and Braille System
Q45. Name the main parts of the human eye involved in vision.
Ans. The main parts are the cornea, iris, pupil, eye lens,
retina and the optic nerve. Together they help form and carry images to the brain.
Q46. What is the function of the iris and pupil in the eye?
Ans. The iris is the coloured part of the eye; it controls the size of the pupil.
The pupil is the opening through which light enters the eye. Together they regulate the amount of light entering the eye.
Q47. How is the image formed in our eye and how do we actually “see” it?
Ans. The eye lens forms a real image of the object on the retina.
The retina converts this image into electrical signals, which are carried by the optic nerve to the brain, where the sensation of vision is created.
Q48. Mention any three ways to take care of our eyes.
Ans. (i) Read and write in good light, not in very dim or very bright light.
(ii) Do not watch TV or mobile screens from very close distances.
(iii) If there is irritation, pain or blurred vision, visit an eye specialist instead of rubbing the eyes.
Q49. What is the Braille system and who invented it?
Ans. The Braille system is a method of reading and writing used by visually impaired persons,
in which letters are represented by patterns of raised dots. It was invented by Louis Braille.
Q50. How does Braille help visually impaired learners to study subjects like Science?
Ans. In Braille books, text, numbers and important symbols are written as raised dot patterns.
Visually impaired learners read these patterns by touch, allowing them to understand concepts, learn definitions and solve problems like other students.
Conclusion
This topic-wise set of 50 Short Answer Questions with clear solutions for
Chapter 16 – Light covers all key NCERT concepts: reflection, plane mirrors, multiple reflection,
colours and the human eye. Regular practice of these questions will strengthen your understanding and
boost your performance in CBSE Class 8 Science exams.