PHYSICS

 Q: Fog/ cloud appears white. Why ? Ans: Light is scattered by the fog particles. As the size of the particles is bigger than the wavelength of light, all colours are scattered to equal extent giving back white light.  The property of light responsible for white clouds: scattering of light.

 Convex lens can behave as a concave lens and vice versa when the lens is placed in a medium with refractive index more than that of the lens. Convex lens diverges and concave converges the rays.

Ans:  The replica of an object  formed by the intersection of reflected rays is called an image. Image is formed when the reflected rays actually meet at a point        ( real image)or appear to meet( virtual image)

 ABSOLUTE  REFRACTIVE INDEX  The absolute refractive index of a medium is the ratio of speed of light in vacuum and the speed of light in the medium. Absolute refractive index = Speed of light in vacuum or air                                                     Speed of light in the medium  For example, A.r.i of glass = speed of light in vacuum/speed of light in glass  3×10⁸/2×10⁸= 3/2=1.5 Its value is equal or more than 1. For vacuum or air, its value is 1. So its minimum value is 1. RELATIVE REFRACTIVE INDEX  The relative refractive index of a medium (a) with respect to another medium (b) is the ratio of speed of light in medium (b) and the speed of light in medium (a). Relative refractive index of  (a) wrt (b)=Speed of light in medium (b )                        ...

 Answer:  Inner pulleys are smaller than others to eradicate the frictional force between the ropes and inner pulleys while in use.

Spanner has a long handle. Why? Answer: When perpendicular distance between the force and the axis of rotation is large, smaller force is required to produce  the desired torque.

Terminal voltage of a dry cell is 1.3 V. It means that the cell can supply 1.3J of energy to move unit positive charge across its terminals in the external circuit connected to the cell.