What makes things visible - class-VI

The reflection from a concrete sidewalk is a diffused reflection yes it is true as they are not a perfect reflecting surface.

ARROWS are used to specify the direction of propagation of a light.

Luminous objects are those which emit their own light. For example, sun and stars.

Self-luminous bodies are those bodies that produce light of their own.
Sun has its own light.

Sun is a natural source of light, which emits light of its own.

Light is:
(i) An electromagnetic radiation
(ii) A transverse wave
(iii) Massless

A source of light is any device serving as a source of illumination;

A burning candle produces light of its own

Earth doesn't have light of its own

The amount of light reflected depend upon the properties of the material and the surface polished.Hence reflection depends upon the smoothness of the material at which light is incident.

Heat is a form of energy which causes sensation of warmth or coldness whereas light is form of energy which helps us in our vision of objects.

Twilight on Earth is the illumination of the lower atmosphere when the Sun itself is not directly visible because it is below the horizon. Twilight is produced by sunlight scattering in the upper atmosphere, illuminating the lower atmosphere so that Earth's surface is neither completely lit nor completely dark.

It is a luminous object rest all are non-luminous

Natural sources of light are the sources which emit light on their without any man made control.Example sun,stars etc.

A plane mirror is made from a few mm thick glass plate.one surface of glass plate is polished to a high degree of smoothness which forms the front part of the mirror and the other(back)surface is silvered(I.e painted with silver,mercury or some other material.)

Light is a form of energy which does not require any medium to travel.

An object is visible to us only if light reflected or emitted by it reaches our eye and image is formed at retina.

The intensity of the light is decreased because no surface is perfectly reflecting surface. When the light is incident on a reflecting surface some part of the light is observed, resulting in decrease in the intensity.

False

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

Sun is a luminous object because it a source of light and consequently emits light of it's own.
Moon is a non-luminous object because it does not emits it's own light and glows by reflecting the light of the sun.

Hence, the correct answer is OPTION C. 

Luminous objects can be defined as objects which emit their own light by use of some reactions or energy source.

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. 

$\begin{array}{l} i+r=i+i=140 \ or, , i={ 70^{ 0 } } \end{array}$

Light is electromagnetic radiation that is visible to the human eye and is responsible for the sense of vision.

Projector act as a point source

Light travels through vacuum for sure as it does not need a material medium for its propagation. Sunlight is the biggest example for this.

A single wave of light is called a ray.

The wavelength of visible light lies between $400\,{\rm{nm}}$ to $800\,{\rm{nm}}$.

Or, $4 \times {10^{ - 7}}$ to $8 \times {10^{ - 7}}\,{\rm{m}}$

Here when second order minica replaces bright spot change in path difference$3\pi $