Physics Class 11&12 questions टेलीग्राम पोस्ट

Optical-Instruments.pdf

The cloud is composed of dust particles and molecules of water. These particles are large and do not obey the law of scattering. Therefore all the colors are scattered equally. So the clouds are white. At sunrise or sunset, sunlight has to travel through the atmospheric air for longer distance. As a result, a large number of air particles come in its way. These particles scatter most of the blue light and make the sun look orange and red.

Sometimes we wonder why the sky appears blue? Since the wavelength of the blue color is smaller than the wavelength of the red color, the scattering of the blue light by the particles in earth’s atmosphere is very large. Although the violet light is scattered more than the blue light, our eyes are not very sensitive to violet light. This is the reason we see the sky as blue.

• Scattering of Light:
When we enter a dark room, usually we cannot see the path of light. But with the help of the laser beam, we are able to see the path. This is due to the scattering of light by small particles of air in the path of the laser beam. The phenomenon in which the path of the light incident on the particle is redirected in a different direction is called the scattering of light. Light of shorter wavelengths is scattered much more than the light of longer wavelengths.

Reflection of Rays from a Spherical Mirror

The Laws of Reflection :

• The angle of incidence is equal to the angle of reflection.

• The incident ray, the normal and the reflected ray, all lie in the same plane.

• The reflected ray and the incident ray are on the opposite sides of the normal.

There are two types of reflection :

1) Regular Reflection : It is a mirror-like reflection of rays of light. Here the rays of light which are reflected from a smooth and shiny object such as a mirror, are reflected at a definitive angle and each incident ray which is reflected along with the reflected ray has the same angle to the normal as the incident ray.

2) Diffused Reflection :
This is a non-mirror-like reflection of light. In this type of reflection rays of light hit an irregular object with a rough surface, and reflects back in all directions. Here, the incident ray which is reflected along with reflected ray doesn’t have the same angle to the normal as the incident ray.