Get the simplified Class 7 Science Extra Questions and Class 7th Curiosity Chapter 11 Light Shadows and Reflections Important Extra Question Answer with complete explanation.
Class 7 Science Chapter 11 Light Shadows and Reflections Extra Questions
Class 7 Science Chapter 11 Extra Questions on Light Shadows and Reflections
Light Shadows and Reflections Class 7 Very Short Question Answer
Question 1.
Give the form of energy that produces the sensation of vision.
Answer:
Light is the form of energy which produces the sensation of vision.
Question 2.
The moon appears bright in the night sky. Is it a luminous object?
Answer:
No, it reflects light from the sun.
Question 3.
On a sunny day, does a bird or an aeroplane flying high in the sky cast its shadow on the ground? Under what circumstances, can we see their shadow on the ground?
Answer:
No, they do not cast any shadow on the ground because they are too high. They can cast shadow only. If they are at some lower height, i.e. if they are near to the ground.
Question 4.
A glass tumbler does not cast a dark shadow like a book does. Why?
Answer:
Because glass is transparent and allows light to pass through it while a book is an opaque object.
Question 5.
When you place a ball in sunlight, you observe a dark patch behind it. What is this dark patch?
Answer:
The dark patch is a shadow.
Question 6.
Observe the picture given in figure. A sheet of some material is placed at position P, still the patch of light is obtained on the screen. What is the type of material of this sheet?
Answer:
The material is transparent glass because only a transparent medium can pass light through it completely and the light will be seen on the screen.
Question 7.
Briefly mention what makes things visible to us.
Answer:
When a light ray after getting reflected by an object falls on our eyes, it allows us to see things around us.
Question 8.
Briefly tell that how many reflected rays can be obtained from a single incident ray with respect of a plane mirror?
Answer:
For a single incident ray, there will be only one reflected ray that can be obtained with respect of a plane mirror.
Question 9.
What makes us see ourselves, when we stand in front Of a mirror?
Answer:
The reflected light coming from our body is again reflected by the mirror and reaches to our eyes which enables us to see ourselves when we stand in front of it.
Question 10.
State the size of image formed by a plane mirror.
Answer:
The size of image formed by a plane mirror is same as that of the object in front of the mirror.
Question 11.
Mention the five English letters that do not show lateral inversion on suffering reflection from a plane mirror.
Answer:
The five English letters which do not show the lateral inversion on suffering reflection are A, H, O, T, U.
Question 12.
Mention the name of device that is generally used by the designers of wallpapers and fabrics.
Answer:
Kaleidoscope is a device that is generally used by the designers of wallpapers and fabrics.
Light Shadows and Reflections Class 7 Short Question Answer
Question 1.
Three torches A, B and C shown in figure are switched ON one-by-one. The light from which of the torches will not form a shadow of the ball on the screen?
Answer:
The light from the torch C will not form a shadow on the screen because there is no screen placed in fronat of the torch C.
Question 2.
A mug was placed between a torch and a screen.The picture shows the shadows of the cup at different positions of the cup.
Choose Yes or No for the correct response.
| What does the picture show? | Yes or No |
| The size of a shadow depends on the distance of the object from the light source. | Yes/No |
| The shape of a shadow depends on the distance of the object from the screen. | Yes/No |
| The size of a shadow depends on the screen size. | Yes/No |
Answer:
| What does the picture show? | Yes or No |
| The size of a shadow depends on the distance of the object from the light source. | Yes |
| The shape of a shadow depends on the distance of the object from the screen. | No |
| The size of a shadow depends on the screen size. | No |
Question 3.
We need a shiny surface for reflection. Explain why?
Answer:
The extent of reflection depends upon the shine and smoothness of the surface. Greater the shine and smoothness of the surface, greater will be the reflection. So, this is the reason why we require a shiny surface for reflection.
Question 4.
Draw figure showing the position of the plane mirror. Also, label the angle of incidence and angle of reflection on it.
Answer:
Question 5.
Assume, a person is standing in front of a plane mirror. The distance between the mirror and his image is 6m. If the person moves 2 m towards the plane mirror, what would be the distance between the person and his image?
Answer:
The image is 6 m away from the plane mirror. It means that the object is also 6 m away from the mirror.
When the person moves 2 m towards the plane mirror, then the distance between the person and the plane mirror will be equal to (6 m – 2 m) = 4 m, this means that distance between the image and the mirror will be 4 m
The distance between the person and his image
= PO’ + Pr’ = 4 + 4 = 8m
Question 6.
Look at figure. Can the image of the child in it be Obtained on a screen?
Answer:
The image of the child cannot be obtained on the screen because the image is not real. The images formed by plane mirror are virtual, and virtual images cannot be captured on a screen.
Question 7.
What is a virtual image? Give one situation where a virtual image is formed.
Answer:
An image which cannot be obtained on a screen is called a virtual image. The image formed by a plane mirror is virtual image because it cannot be obtained on a screen.
Question 8.
Mention any two letters of English alphabet whose image formed in a plane mirror appears exactly similar to the letters.
Answer:
Image formed by the plane mirror shows lateral inversion, i.e. left seems to right or vice-versa. But in the case of alphabets like A and H there is no lateral inversion.
Question 9.
Explain the term lateral inversion.
Answer:
When an image is formed by a plane mirror, then the left side of image is object’s right side and right side of image is object’s left side. This process of change in the sides of the image w.r.t. the object is known as lateral inversion.
Question 10.
Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Answer:
Image of letters of English alphabet such as A, H, I M, O, T, U, V, W, X, Y formed in a plane mirror appears exactly like the letter itself. Since, these letters are symmetric in nature, hence they don’t show lateral inversion.
Question 11.
Why the word AMBULANCE is written laterally inverted on AMBULANCE vehicle?
Answer:
The word AMBULANCE is written laterally inverted on ambulance vehicle because when the driver of a vehicle ahead of an ambulance looks in her/his rear view mirror, she/he can read “AMBULANCE” written on it and give way to it.
Question 12.
In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Answer:
An image is formed due to the reflection of light by a plane mirror. In a completely dark room, there is a no light present. Thus, no reflection of light takes place by the mirror placed in the room.
Hence, no image will be formed by a mirror in a completely dark room.
Light Shadows and Reflections Class 7 Long Question Answer
Question 1.
There is a mistake in each of the following ray diagrams given as figure (a), (b), and (c). Make the necessary correction(s).
Answer:
The correct diagrams are as below
Question 2.
A man stands 10 m in front of a large plane mirror, so how far must he walk before he is 5 m away from his image?
Answer:
As, per the given information, point O is initial position of the man and / is initial position of the image of the man which can be shown with the help of a figure.
Point O’ is final position of the man and I’ is final position of the image of the man. From the figure,
O’P + PI’= 5m [0’P = PI’]
=> O’P + 0’P = 5m =
=> 0’P = 25m
Distance walked by the man = OP – O’P
= 10 – 2.5 = 7.5m
Question 3.
Figure shows the word REST written in two ways in front of a mirror. Show how the word would appear in the mirror?
Answer:
According to reflection properties of plane mirror, it forms same size, laterally inverted images of the object in front of them.
Question 4.
Boojho planned an activity to observe an object A through pipes as shown in figure, so that he could see objects which he could not directly see.
(i) Mention how many mirrors should he use to see the objects?
(ii) Indicate the positions of the mirrors in the figure.
(iii) State what must be the angle w.r.t. the incident light at which he should place the mirrors?
(iv) Indicate the direction of rays in the figure of (ii) Part.
(v) If any of the mirrors is removed, will he be able to see the Objects?
Answer:
(i) Number of mirrors required = 3
(ii) Positions of the mirrors are as shown in figure
(iii) Mirrors should be placed at 45° w.r.t. the incident light.
(iv) Direction of rays is shown in figure by arrows.
(v) He will not be able to see the objects if any of the mirrors is removed.
Question 5.
How is the phenomenon of reflection used in making a kaleidoscope. What are the applications of a kaleidoscope?
Answer:
Kaleidoscope is a cylinder with three mirrors containing loose, coloured objects such as beads or pebbles and bits of glasses. As the viewer looks into one end, light entering the other creates a colourful pattern due to reflection. Its applications are given below
(i) It works on the principle of multiple reflections, where several mirrors are placed at an angle (usually 60°) to one another. Typically, these are three rectangular mirrors set at 60° to each other, so that they form an equilateral triangle.
(ii) The 60° angle creates seven duplicate images of the objects, 5 at 60° and 2 at 90°. As the tube is rotated, the tumbling of the coloured objects present varying colours and patterns.
(iii) It is used in decoration purposes, attractive toys, etc.
Light Shadows and Reflections Class 7 Case Based Questions
Question 1.
The picture shows a light ray from a candle falling on a mirror. P, Q, R, S and Tare five points behind the mirror.
Answer the following questions based on the above information.
(i) Which arrow represents the light ray reflected by the mirror?
(a) Arrow 1
(b) Arrow 2
(c) Arrow 3
(d) Arrow 4
Answer:
(c) Arrow 2 is normal to the mirror.
Hence,by measuring angle between incident ray and arrow 2 and between arrow 2 and arrow 3, we conclude that arrow 3 is the reflected ray.
(ii) At which point, will the image of the candle form? Will the image be erect or inverted ?
Answer:
Extend the arrow 3 behind the mirror. It will meet to Q. Hence, image will be formed at Q.
Plane mirror always forms the image in the same size as the object. Since, the object is erect, hence the image will also be erect.
Question 2.
Ayan made a periscope using a cardboard box and two plane mirrors set at an angle. His friend Meera brought a kaleidoscope, she made using three mirrors and colorful beads. They compared how both devices worked and observed different effects through them.
(i) Which device helps to see objects that are not directly visible and how?
Answer:
The periscope helps to see objects that are not directly visible. It uses two plane mirros placed at 45° angles to reflect light from the object and make it visible to the viewer’s eyes.
(ii) Why do beautiful patterns form in a kaleidoscope?
Answer:
Beautiful patterns form in a kaleidoscope due to multiple reflections of colored beads between three plane mirrors arranged in a triangular shape.
Light Shadows and Reflections Class 7 Skill Based Questions
Question 1.
The given figure shows a girl standing at a position A in front of a plane mirror, at a dstance of a metre from the mirror. When she moves b metre away to a new position B, the distance between the girl and her image increases by 8 m. What is the value of b?
(a) 2 m
(b) 4 m
(c) 8 m
(d) Data is not sufficient
Answer:
(b) The girl is initially at position A, at a distance of a metres from the mirror. Her image will also be a metres behind the mirror.
So, the initial distance between the girl and her image
= a + a = 2a metres.
When she moves b metres to position B. her new distance from the mirror becomes (a + b) metres, and her image will be the same distance behind the mirror.
So, the new distance between the girl and her image
=(a + b)+(a + b) = 2(a + b) metres
According to the question, the distance between the girl and her image increased by 8 metres.
∴ 2(a + b) — 2a = 8
2a + 2b — 2a = 8
2b = 8
b = 4m
Question 2.
A student studies that a plane mirror results in a laterally inverted image after reflecting. Which of these represents the image likely to be formed by a plane mirror?
Answer:
The image that is likely to be formed by a plane mirror is option (c), where the object is laterally inverted in the Image, appearing as 51. This is because plane mirrors produce images that are virtual, upright and Laterally inverted. Lateral inversion means the left and right sides of the object are reversed in the image.
Question 3.
When we pass under a tree covered with large number of leaves, we notice small patches of sunlight under it. These
circular Images are, in fact pinhole images of the Sun. The gaps between the leaves, act as the pinholes. These gaps
are all kinds of Irregular shapes, but we can see circular images of the Sun. This is called natural pinhole camera.
(i) Which of the following acts as pinhole in the natural pinhole camera?
(a) Leaves act as pinhole
(b) Gaps between the leaves
(c) Water droplets
(d) None of the above
Answer:
(b) Gaps between the lenses
The tiny gaps between the lenses allow only a small beam of light to pass through, which creates a natural pinhole effect and projects an inverted image of the Sun on the ground.
(ii) What is required to create the pinhole camera?
(a) Cardboard
(b) Tracing paper
(c) Lens
(d) Mirrors
Answer:
(a) Cardboard
To make a pinhole camera, a small hole is made in an opaque material (commonly cardboard) to allow light from an object to pass through and form an image on the opposite side (usually a screen or film). No lenses or mirrors are used in a basic pinhole camera.
Light Shadows and Reflections Extra Questions for Practice
Question 1.
What type of image is formed by a plane mirror?
Question 2.
Explain lateral inversion with an example.
Question 3.
Why can’t the image formed in a plane mirror be obtained on a screen?
Question 4.
State any two observations from everyday life which show that light travels in straight line.
Question 5.
Why does the size of a shadow change during the day?
Question 6.
What would happen if the mirrors in a periscope are not placed at 45° angles?
Question 7
Explain with a diagram how lateral inversion occurs in a plane mirror. How does it affect the image of alphabets and numbers?
Question 8.
How does changing the size of the pinhole or distance between the pinhole and screen affect the image in a pinhole camera? Explain with reason.
Question 9.
How can a kaleidoscope be used to study the principles of reflection and symmetry? Describe its applications in real life.