Light and Sound
1) Those
objects which emit light are called luminous objects. Example Sun, bulb, candle.
2) Those
objects which do not emit light or only be seen when light
is reflected from them is called Non luminous object. Example moon, earth.
3) On the base of optical
properties, Objects are classified into opaque, transparent and translucent.
4) Opaque: If you cannot see through an object then the object is opaque because
opaque materials do not allow light to pass through them.
5) Translucent: We cannot clearly see through the object then the
object is translucent objects. Example wax paper, tissue
6) Transparent object: The object through which we can see clearly. Example: air, glass,
water.
7) Light travels in a straight line. When its path is blocked
by an opaque object then a shadow is formed.
8) Pinhole camera works on the principle that light travels in
a straight
line.
9) The Sun is the largest
natural source of light.
10) Moon is non-luminous object.
11) Sun is luminous object.
MCQs
The ……. is the largest natural source of light?
a) Moon
b) Satellite
c) Sun
d) Star
The speed of light in vacuum is…..
NTS Past ----CT Test
a) 300,000 km/s
b) 400,000 km/s
c) 500,000 km/s
d) 600,000 km/s
Fastest thing in universe is;
a) Light
b) Sound
c) Heat
d) All of these
Such objects, which emit light, are called …… objects.
a) Bright
b) Luminous
c) Non-luminous
d) Transparent
