NCERT SOLUTIONS FOR CLASS 7 SCIENCE LIGHT CHAPTER 15
Q.1.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.
Q.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 form a real image. (T/F)
(i) Plane mirror forms an erect image. (ii) It forms a virtual image. (iii) Size of the image is the same as that of the object. (iv)Image is formed at the same distance behind the mirror as the object stands in front of it. (v) Image formed is a laterally inverted image i.e., the right-hand side of the object seems to be the left-hand side and vice-versa.
Q.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.
The image which cannot be taken on a screen is called 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 image is called virtual image.
Q.7. State two differences between a convex and a concave lens.
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 side-view mirror in vehicles
Q.12. David is observing his image in a plane mirror. Die 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
Q.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 rear mew 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