Gujarat Board GSEB Textbook Solutions Class 7 Science Chapter 15 Light Textbook Questions and Answers, Notes Pdf.
Gujarat Board Textbook Solutions Class 7 Science Chapter 15 Light
Gujarat Board Class 7 Science Light Textbook Questions and Answers
Question 1.
Fill in the blanks:
(a) An image that cannot be obtained on a screen is called ………….
(b) The image formed by a convex ………….. is always virtual and smaller in size.
(c) An image formed by a …………. mirror is always of the same size as that of the object.
(d) An image which can be obtained on a …………… screen is called an image.
(e) An image formed by a concave …………. cannot be obtained on a screen.
Answer:
(a) virtual image
(b) mirror
(c) plane
(d) real
(e) lens
Question 2.
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
(b) A concave lens always forms a virtual image. (T/F)
(c) We can obtain a real, enlarged, and inverted image by a concave mirror. (T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always forms a real image. (T/F)
Answer:
(a) False
(b) True
(c) True
(d) False
(e) False
Question 3.
Match the items given in Column I with one or more items of Column II.
| Column A | Column B |
| (a) A plane mirror | 1. Used as a magnifying glass. |
| (b) A convex mirror | 2. Can form an image of objects spread over a large area. |
| (c) A convex lens | 3. Used by dentists to see enlarged images of teeth. |
| (d) A concave mirror | 4. The image is always inverted and magnified. |
| (e) A concave lens | 5. The image is erect and of the same size as the object. |
| 6. The image is erect and smaller in size than the object. |
Answer:
| Column A | Column B |
| (a) A plane mirror | 5. The image is erect and of the same size as the object. |
| (b) A convex mirror | 2. Can form image of objects spread over a large area. |
| (c) A convex lens | 1. Used as a magnifying glass. |
| (d) A concave mirror | 3. Used by dentists to see enlarged images of teeth. |
| (e) A concave lens | 6. The image is erect and smaller in size than the object. |
Question 4.
State the characteristics of the image formed by a plane mirror.
Answer:
- The plane mirror forms an erect image,
- It forms a virtual image.
- The size of the image is the same as that of the object.
- The image is formed at the same distance behind the mirror as the object stands in front of it.
- The image formed is a laterally inverted i.e., the right-hand side of the object seems to be the left-hand side and vice-versa.
Question 5.
Find out the letters of the 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:
Letters like A, H, I, M, O, T, U ,V, W, etc. appear the same when seen through a plane mirror.
Question 6.
What is a virtual image? Give one situation where a virtual image is formed.
Answer:
The image which cannot be taken on a screen is called a virtual image. When some object is placed very close to the concave mirror we don’t get any image on the white screen placed behind the mirror. Such an image is called a virtual image.
Question 7.
State two differences between a convex and a concave lens.
Answer:
Convex lens:
- A convex lens can form both real and virtual images.
- It can form a magnified image.
Concave lens:
- A concave lens always forms a virtual image.
- The image is always diminished in size.
Question 8.
Give one use each of a concave and a convex mirror.
Answer:
Use of concave mirror:
A concave mirror is used by dentists to examine the teeth.
Use of convex mirror:
A convex mirror is used as a side-view mirror in vehicles.
Question 9.
Which type of mirror can form a real image?
Answer:
The concave mirror can form a real image.
Question 10.
Which type of lens forms always a virtual image?
Answer:
A concave lens always forms a virtual image.
Choose the correct option
Question 11.
A virtual image larger than the object can be produced by a
(i) concave lens
(ii) concave mirror
(iii) convex mirror
(iv) plane mirror
Answer:
(ii) concave mirror
Question 12.
David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be
(i) 3 m
(ii) 5 m
(iii) 6 m
(iv) 8 m
Answer:
(iii) 6 m
Question 13.
The rearview mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rearview mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be
(i) 1 m/s
(ii) 2 m/s
(iii) 4 m/s
(iv) 8 m/s
Answer:
(ii) 4 m/s
Extended Learning Activities And Projects
Question 1.
Play with a mirror
Write your name with a sketch pen on a thin sheet of paper, polythene or glass. Read your name on the sheet while standing in front of a plane mirror. Now, look at your image in the mirror.
Answer:
Do it yourself.
Question 2.
A burning candle in water Takes a shoebox, open on one side. Place a small lighted candle in it. Place a clear glass sheet (roughly 25 cm) in front of this candle (Fig.). Try to locate the image of the candle behind the glass sheet. Place a glass of water at its position. Ask your friends to look at the image of the candle through the sheet of glass. Ensure that candle is not visible to your friends. Your friends will be surprised to see the candle burning in the water. Try to explain the reason.
Answer:
The plane glass sheet is transparent so the image of a burning candle is formed behind the glass sheet. We see a burning candle behind the sheet. When we put the glass filled with water then the image of a burning candle appears to be in it. So friends see burning candles in water.
Question 3.
Make a rainbow Try to make your own rainbow. You can try this project in the morning or in the evening. Stand with your back towards the sun. Take a hosepipe or a water pipe used in the garden. Make a fine spray in front of you. You can see the different colors of the rainbow in the spray.
Answer:
Do it yourself.
Question 4.
Visit a laughing gallery in some science center or a science park or a village meal. You invillfind some large mirrors. there. You can see your distorted and funny images in these mirrors. Try to find out the kind of mirrors used there.
Answer:
Students write the answer or tell the kind of mirror with their own experiences.
Question 5.
Visit a nearby hospital. You can also visit the clinic of an ENT specialist or a dentist. Request the doctor to show you the mirrors used for examining the ear, nose, throat, and teeth. Can you recognize the kind of mirror used in these instruments?
Answer:
The kind of mirror used for examining ear, nose, throat, and teeth are concave mirrors.
Question 6.
Roleplay
Here is a game that a group of children can play. One child will be chosen to act as an object and another will act as the image of the object. The object and the image will sit opposite to each other. The object will make movements, such as raising a hand, touching an ear. etc. The image will have to make the correct movement following the movement of the object.
The rest of the group will watch the movements of the image. If the image fails to make the correct movement, she/he will be retired. Another child will take her/ his place and the game will continue. A scoring scheme can be introduced. The group that scores the maximum will be declared the winner.
Answer:
Do it yourself.