Physics
Explain the following terms.
(a) Annular solar eclipse
(b) Propagation of light
(c) Transparent material
(d) Parallel beam of light
(e) Scattering of light
Answer
(a) Annular solar eclipse: When the sun and the moon are exactly in line, but the sun is not completely covered by the moon because the apparent size of the moon is smaller than that of the sun as seen from the earth so, a bright ring of light known as the corona is visible around the central circular dark region of the moon and this phenomenon is called annular solar eclipse.
(b) Propagation of light: Light always propagates in a straight line in a medium such that the path traversed by light in a medium between any two points is the shortest so light takes minimum time in travelling from one point to another and this property of light travelling in a straight line is known as rectilinear propagation of light.
(c) Transparent material: A material which allows light to pass through it completely so that an object is clearly visible when viewed through it, is called a transparent material. Examples are glass, air and water.
(d) Parallel beam of light: When a number of rays move parallel to each other, the beam is called a parallel beam of light. It is produced by a distant source of light like the sun.
A parallel beam is shown below :
(e) Scattering of light: : The phenomenon of the deflection of light from its straight path by particles of a medium such that some of the light is absorbed and re-emitted in different direction is called scattering of light.
Related Questions
Give reasons for the following statements.
(a) A table does not emit any light.
(b) Light does not completely pass through a coloured bottle.
(c) A glass does not cast any shadow.
(d) The length of shadows depends on the time of the day.
(e) The size of the shadow depends on the size of the light source.
Match the columns.
Column A Column B 1. Nature of image formed by pinhole camera (a) Grey zone of a shadow 2. Lunar eclipse (b) Dark shadow 3. Example of penumbra (c) Inverted image 4. Luminous object (d) Full moon night 5. Shadow formed by opaque object (e) LEDs Differentiate between luminous objects and non-luminous objects. Give examples if applicable.
Differentiate between transparent, translucent and opaque objects. Give examples if applicable.