NCERT Solutions for Class 7th Science
Chapter 15 – LIGHT
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
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.
Ans (a) An image that cannot be obtained on a screen is called _virtual_.
(b) Image formed by a convex _mirror_ is always virtual and smaller in size.
(c) An image formed by a _plane_ 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 _real_ image.
(e) An image formed by a concave _lens_ 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 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)
Ans (a) We can obtain an enlarged and erect image by a convex mirror. (F)
Correct: Image formed by a convex mirror is always virtual, erect and diminished.
(b) A concave lens always form a virtual image. (T)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T)
Q.3 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.
Ans Column I Column II
(a) A plane mirror (v) The image is erect and of the
same size as the object.
(b) A convex mirror (ii) Can form image of objects
spread over a large area.
Q.4 State the characteristics of the image formed by a plane mirror.
Q.5 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.
Ans The alphabets A,H,I,M,O,T,U,V,W,X,Y will have the images exactly like themselves. This is because they are vertically symmetrical i.e. if a vertical line is drawn in middle of the alphabets, the two halves will be identical.
Q.6 What is a virtual image? Give one situation where a virtual image is formed.
Ans An image that cannot be obtained on a screen is called a virtual image. An object placed in front of a plane mirror will have a virtual image as it cannot be obtained on a screen.
Q.7 State two differences between a convex and a concave lens.
Q.8 Give one use each of a concave and a convex mirror.
Q.9 Which type of mirror can form a real image?
Q.10 Which type of lens forms always a virtual image?
Q.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
Q.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
Q.13 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