PHYSICS [3 Mark Question Answer]

Primary colours:
1.If we break the white colour we can get the seven colours. Red, Orange, Yellow, Green, Blue, Indigo, Violate.
2.But among the seven colours their are three colours Red, Blue and green can produce white light. Those are called Primary colours.
3.Primary colours are permanent colours which can not be obtained by mixing two or more different colours.
Secondary colour:
1.By mixing two unlike primary colours we can get obtained the secondary colour.
2.The colours are
• Red + Blue = Magenta
• Blue + Green = Cyan
• Red + Green + Yellow

Four uses of plane mirrors:
• They are used as looking glass.
• They are used in solar cookers.
• They are also used in constructing periscope which is used in submarines.
• They are also used to make kaleidoscope, a toy which produces beautiful patterns.

Four characteristics of the images formed by plane mirrors are as follows:
• The images are of the same size as that of the objects.
• The images are formed behind the mirrors at the same distance from the mirrors as that of the objects.
• The images formed are virtual and erect.
• The images are laterally inverted.

When a beam of parallel light rays is incident on a rough surface, the reflected rays scatter in different directions. This type of reflection is called irregular or diffuse reflection. In this case, the angle of reflection of the light is equal to the angle of incidence. Reflection from a rough surface is called diffuse reflection.
Name two materials from which irregular reflection takes place – wall, wood, a piece of wool.
The importance of irregular reflection for an object to be seen, it must reflect light irregularly.

When a beam of parallel light rays is incident on a smooth and plane surface, the reflected rays will also be parallel. This type of reflection is called Regular Reflection. In this case, the angle of reflection of the light is equal to the angle of incidence and on the opposite side of the normal to the point of incidence. Reflection from a polished surface is called regular reflection.
Name two materials from which regular reflection takes place – a sheet of stainless steel and a thin sheet of aluminum.
The importance of regular reflection offers clear and sharp images, is essential in optical devices and signal transmission, and aids in scientific research.