The dark coloured patch formed on the screen opposite to the light by an opaque object is called shadow. For the formation of a shadow, a source of light, an opaque object and a screen are required. Shadow is formed by an opaque object when light falls on it. Its size and shape change according to direction of light or orientation of object. It can be large or small than the object. During morning and evening shadow is larger. It is smaller during noon. The colour of shadow is dark irrespective of the colour of object. Shadows are not formed in dark i.e. in absence of light. The shadows are not uniformly dark. Central inner part is darker than outer surrounding part. The darker part of shadow is called umbra and less dark part is called penumbra. There is no change of left part of object to right part of image and right part of object to left part of image.
In nature, lunar eclipse and solar eclipses are examples of shadow formation.
Q.1 Among the followings options which is not always necessary for shadow formation?1
(a) The sun
(b) A screen
(c) An Opaque object
(d) A source of light
Q.2 Harshit observed his shadow at 9:00 A.M., 12:00 Noon and 3:00 P.M. Which among the following statements is correct about his observation of shadow? 1
(a) His shape changes but size remains same.
(b) His size changes but shape remains same.
(c) Both shape and size of his shadow change.
(d) Neither shape nor size of his shadow change.
Q.3 Four shirts of red, blue, green and yellow colour are hanging on a clothes line in the sun. What will be the colour of their shadows? 1
(a) Their shadows will be red, blue, green and yellow.
(b) Their shadows will be light dark in colour.
(c) Their shadows will be light red in the sunlight.
(d) Their shadows will be purple in colour.
Q.4 Which of the following statements is true about umbra and penumbra of a shadow? 1
(a) Umbra is comparatively darker than penumbra
(b) Penumbra is comparatively darker than umbra
(c) Umbra is same as penumbra in darkness.
(d) Umbra is comparatively lighter than penumbra.
Q.5 In an activity four torches A, B, C and D were switched on an apple. Looking their position which position, which torch or torches will not form their shadow on the screen? 1
(a) Torch A
(b) Torch C
(c) Torch D
(d) Both Torch C and D
Q.6 Which among the following objects will never form a circular shadow? 1
(a) A football
(b) A flat circular disc
(c) A cylindrical metal rod
(d) A rectangular box
Q.7 What will be the conditions of formation of Solar eclipse? 2
Ans.-1 (a) The sun
Ans.-2 (c) Both shape and size of his shadow change.
Ans.-3 (b) Their shadows will be light dark in colour.
Ans.-4 (a) Umbra is comparatively darker than penumbra
Ans.-5 (d) Both Torch C and D
Ans.-6 When the Moon comes in between the Sun and the Earth in a straight pathway, solar eclipse is formed.