Chapter Review:

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• Light travels along straight lines.
• Mirror changes the direction of light  This change of direction by a
  mirror is called reflection of light.
• In an image formed by a mirror, the left side of the object is seen on the right side in the image, and right side of the object appears to be on the left side in the image.
• If the reflecting surface of a spherical mirror is concave, it is called a concave mirror.
• If the reflecting surface is convex, then it is a convex mirror.
• An image formed on a screen is called a real image.
• The image formed by a plane mirror could not be obtained on a screen. Such an image is called a virtual image.
• Concave mirror form a real image.
• Image formed by a convex mirror is erect, virtual and smaller in size
  than the object.
• Those lenses which feel thicker in the middle than at the edges are convex lenses.
• Those which feel thinner in the middle than at the edges are concave lenses.
• A concave lens always forms erect, virtual and smaller image than the
  object.
• When seven colours of rainbow pasting on the disk in their order rotates in daylight it seems white. Such disk is generally known as Newton’s disk.
• White light is composed of seven colours.

Exercise 

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Q1. Fill in the blanks:

(a) An image that cannot be obtained on a screen is called ____________.

(b) 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 a _________ image.

(e) An image formed by a concave ___________ cannot be obtained on a screen.

Answer: 

(i) Vertual image

(ii)  miror

(iii) plane

(iv) real 

(v) lens

Q2. 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 form 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 form a real image. (T/F)

Answer: 

(a) False

(b) True

(c) True

(d) False

(e) False

Q3. Match the items given in Column I with one or more items of Column II.

Column I             Column II

(a) A plane mirror    (i) Used as a magnifying glass.

(b) A convex mirror  (ii) Can form image of objects spread over a large                         area.

(c) A convex lens    (iii) Used by dentists to see enlarged image of                              teeth.

(d) A concave mirror (iv) The image is always inverted and magnified.

(e) A concave lens   (v) The image is erect and of the same size as                            the object.

                     (vi) The image is erect and smaller in size than                            the object.

Answer:

Q4. State the characteristics of the image formed by a plane mirror.

Answer: 

Characteristics of the image formed by a plane mirror are as follows:
(i) Images are virtual and erect.
(ii) it's position is behind the mirror.
(iii) Size of image is equal to size of object.
(iv) Laterally inverted image (image of left side visible on right side).
(v) Distance of image behind the mirror is equal to distance of object in front of mirror. 

Q5. 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: 

The letters are A, H, I, M, O, T, U, V, W and X which form same image as the letter is. These letters are laterally symmetrical.

Q6. What is a virtual image? Give one situation where a virtual image is formed.

Answer: The image, which cannot be obtained on a screen, is called virtual image. The images formed by plane mirror, convex mirror and concave lens are always virtual in nature.

Q7. State two differences between a convex and a concave lens.

Answer: 

Q8. Give one use each of a concave and a convex mirror.

Answer: 

(i) Concave mirror is used by dentist, headlights in vehicle, As reflector in a torch, etc.
(ii) Convex mirror is used in rear view mirrors.

Q9. Which type of mirror can form a real image?

Answer: Cocave Mirror forms a real image. 

Q10. Which type of lens forms always a virtual image? Choose the correct option in questions 11–13

Answer:

Concave lens. 

Q11. 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 

Q12. 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

Q13. The rear view 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 rear view 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) 2 m/s 

Additional Questions:

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Ques: What is concave mirror?
Ans: If the reflecting surface of a spherical mirror is concave, it is called a concave mirror.

Ques: What is convex mirror?
Ans: If the reflecting surface is convex, then it is a convex mirror.

Ques: What is real image?
Ans: An image formed on a screen is called a real image.

Ques: What is virtual image?
Ans: The image formed by a plane mirror could not be obtained on a screen. Such an image is called a virtual image.

Ques: Which type of mirror can form a real image?
Ans: Concave mirror. 

Ques: Which type of lens forms always a virtual image?
Ans: Concave lens.

Ques: Give one use each of a concave and a convex mirror.
Ans: 

Use of Concave Mirror- 

(i) In Head-lights of Vehicles

Use of Comcave Mirror-

(i) It is used in vehicles as side mirror.

Ques: What is convex lens?
Ans: Those lenses which feel thicker in the middle than at the edges are convex lenses.
Ques: What is concave lens?
Ans: Those which feel thinner in the middle than at the edges are concave lenses.

Ques: Why is convex lens called converging lens?
Ans: A convex lens converges (bends inward) the light generally falling on it. Therefore, it is called a converging lens. 
Ques: Why is concave lens called diverging lens?
Ans: A concave lens diverges (bends outward) the light and is called a diverging lens. 

Ques: Which lens is used as magnificent lens? 

Ans: convex lens. 

Ques: What is white light?
Ans: The sunlight consists of seven colours. The sunlight is said to be white light.
Ques: Name all colours presence in rainbow in their real order.
                          Or 
Ques: Name all colours consist in white light. 
Ans: red, orange, yellow, green, blue, indigo and violet.
Ques: How many colours are there in white light. 
Ans: seven.

Ques: Fill in the blanks:

(i) An image that cannot be obtained on a screen is called _________.

(ii) Image formed by a convex __________ is always virtual and smaller in size.

(iii) An image formed by a __________ mirror is always of the same size as that of the object.

(iv) An image which can be obtained on a screen is called a _________ image.

(v) An image formed by a concave ___________ cannot be obtained on a screen.

Answer: 

(i) Vertual image

(ii)  miror

(iii) plane

(iv) real 

(v) lens

Additional Questions:

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Ques: Why is this suggested that we should not look directly toward the sun or its image?
Ans: Never look directly towards the sun or its image as it may damage your eyes. You may look at the image of the sun when it is thrown on a screen or a wall.

Ques: Why are convex mirror used mainly in vehicles as side mirror?
Ans: Convex mirrors can form images of objects spread over a large area. So, these help the drivers to see the traffic behind them. 

Ques: Write three uses of concave mirrors?
Ans: Uses of concave mirrors.

(i) it is used by ENT doctors to see the ears, nose and throat and reflect the light.

(ii) The dentist uses it to get enlarge image of teeth.

(iii) The reflectors of torches, headlights of cars and scooters are concave in shape.

Ques: Write the differences between convex and concave lens.
Ans: The differences between convex and concave lens.

convex lens:

(i) It feels thicker in the middle than at the edges.

(ii) A convex lens converges (bends inward) the light.

(iii) It forms real and inverted images. 

concave lens:

(i) It feels thinner in the middle than at the edges.

(ii) A concave lens diverges (bends outward) the light.

(iii) It forms virtual and erect images. 

Ques: Why is word “AMBULANCE” written strangely on Ambulance? 
Ans: When the driver of a vehicle ahead of an ambulance looks in
her/his rear view mirror, s/he can read ‘AMBULANCE’ written on it and give way to it. 

Ques: What is Newton’s Disk? 
Ans: When seven colours of rainbow pasting on the disk in their order rotates in daylight it seems white. Such disk is generally known as Newton’s disk.