Tag: light travels in straight line

Objects which do not emit light on their own are called  $ \bf{non-luminous} $ objects.
Objects that give out or emit light of their own are called as $ \bf{luminous\ objects} $.

Moon is a non-luminous object because it does not emits it's own light and glows by reflecting the light of the sun.
Sun, Bulb and candle give out or emit their own light and hence, are luminous objects.

Hence, the correct answer is OPTION B.

Objects which do not emit light on their own are called  $ \bf{non-luminous} $ objects.
Objects that give out or emit light of their own are called as $ \bf{luminous\ objects} $.

Sun is a source of light and thus, gives out or emits light of it's own and hence, is a luminous object.

Non-luminous objects reflect the light falling on them and the reflected light are sensed by the eye and thus we are able to see non-luminous objects.

Translucent objects allow only a small part of light to pass through them.

A coloured plastic bottle is an opaque material. When a light beam is incident on it, a shadow will form on the screen. Light can easily pass through the transparent material.

Light changes its direction after reflection. As we move the object away from the light source, the shadow becomes larger as the distance between object and the light source increases. Reflection is possible from rough surface also.

We can see things when rays of light coming from any object reach our eyes. So, we cannot see in the dark because of absence of light. 

Ray optics is valid when characteristic dimension are much larger than wavelength of light . The size of obstacle must be much larger than the wavelength of light. If wavelength is comparable to the size of object, then diffraction could happen, but it cannot be explained using ray optics, it will require wave theory of light.