Q37. How can you show the image of the sun on a paper?
Take a concave mirror. Hold it facing the sun. Try to get the light reflected
by the mirror on a sheet of paper. Adjust the distance of the paper until you
get a sharp bright spot on it. This bright spot is, in fact, the image of the
Q38. 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 _________.
image of the truck will travel a distance twice the distance travelled by the
car in equal time. Therefore, image of the truck will appear to approach the
driver with the speed of (2 + 2) m/s i.e. 4 m/s.
Q39. Write an experiment to show that the sunlight consists of
a glass prism. Allow a narrow beam of sunlight through a small hole in the window
of a dark room to fall on one face of the prism. Let the light coming out of
the other face of the prism fall on a white sheet of paper or
on a white wall. We see colours similar to those in a
rainbow. This shows that the sunlight consists of seven colours.
Q40. Why the word ambulance is written laterally inverted on
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. It is the
duty of every one of us to allow an ambulance to pass without blocking its way.
Q41. 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.
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. Vertical
symmetry is found in the letters A, H, I, M, O, T, U, V, W, X and Y. This means
that the right side is a reflection of the left.
Q42. What is the difference between an object and an image?
a lighted candle in front of a plane mirror. Try to see the flame of the candle
in the mirror. It appears as if a similar candle is placed behind the mirror.
The candle, which appears behind the mirror, is the image of the candle formed
by the mirror. The candle itself is the object.
Image from NCERT
Q43. 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 find out the distance between David and his image.
Distance between the mirror and David’s image is 4m.
the David moves 1 m towards the mirror, then the distance between mirror and
David’s image will be (4 – 1) m = 3m
know that in case of plane mirror image is at the same distance behind the
mirror as the object is in front of it. Therefore,
between David and mirror = Distance between mirror and David’s image
Distance between David and his image = Distance between David and mirror + Distance
between mirror and David’s image (i.e. 3 + 3 = 6 m)
Q44. Show that the image is at the same distance behind the plane
mirror as the object is in front of it.
a chess board. Draw a thick line in the middle of it. Fix a plane mirror
vertically on this line. Place a pencil sharpner, at the boundary of the third
square counting from the mirror. Note the position of the image. Now shift the
object to the boundary of the fourth square. Again note the position of the
image. We will find that the image is at the same distance behind the mirror as
the object is in front of it.
Image from NCERT
Q45. Show how light gets reflected from a plane mirror with the
help of an activity.
Take a torch. Cover its glass with a chart paper which has three slits. Spread
a sheet of chart paper on a smooth wooden board. Fix a plane mirror strip
vertically on the chart paper. Now direct the beam of light on the mirror from
the torch with slits. Place the torch in such a way that its light is seen
along the chart paper on the board. Now adjust its position so that the light
from the torch strikes the plane mirror at an angle. We will see that the
mirror change the direction of light that falls on it. Now move the torch
slightly to either side. We will see change in the direction of reflected light
too. Look into the mirror along the direction of the reflected light. We see
the slits in the mirror. This is the image of the slits. This activity shows how
light gets reflected from a plane mirror.
Image from NCERT
Q46. State the differences between a convex and a concave lens.
Difference between a convex and a concave lens
Those lenses which feel thicker in the middle than at the edges are convex
Those lenses which feel thinner in the middle than at the edges are concave
A convex lens converges (bends inward) the light generally falling on it.
Therefore, it is called a converging lens.
A concave lens diverges (bends outward) the light and is called a diverging
A convex lens can form real and inverted image. When the object is placed
very close to the lens, the image formed is virtual, erect and magnified.
A concave lens always forms erect, virtual and smaller image than the object.