Physics (Part-viii) (Railway)

Dispersion is defined as the separation of white light into different colours when the light is passed through the prism.

• The scattering of light depends on the wavelength of the light.

• Therefore, it can be said that the degree of deviation is dependent on the wavelengths.

• The deviation in the path of the light is inversely proportional to the wavelength.

An electric motor converts electrical energy into rotational kinetic energy which is a form of mechanical energy.

• The electric motor works on the principle of electromagnetic induction, which is when a voltage is induced by a changing magnetic field.

• Electric motors are used in electric fans, pumps etc.

Refractive index of a color is inversely proportional to the wavelength of the color.

• Hence, more the wavelength, lesser will be the refractive index.

• So, the arrangement of colors arranged in the increasing order of their refractive indices will be Red Orange < Yellow <Green < Blue < Indigo < Violet.

All the light rays which are parallel to the principal axis of a convex mirror, appear to diverge from the principal focus (F) after reflection from the mirror.

• Parallel rays will diverge from a virtual point behind the mirror one focal length away.

The relation between P, V, R, and I is given by P = I²R

• P is the power delivered by a circuit is the rate of energy transfer (J/s) and is measured in watts (W).

A lens is a piece of transparent glass that concentrates or disperses light rays when passes through them by refraction.

• Water, glass, and cellophane are transparent medium that allows light to transmit through them. So, they can be used for making spherical lenses.

• Wood is an opaque material that cannot transmit light, so it cannot be used to make a lens.

Electrovalent compounds conduct electricity in the molten state.

• This is possible in the molten state since the electrostatic forces of attraction between the oppositely charged ions become weak.

• Thus, the ions move freely and conduct electricity.

The distance between the pole and centre of curvature of a spherical mirror is called radius of curvature.

• The relation between radius of curvature and focal length of a spherical mirror is R = 2f, where R= radius of curvature of the lens and f = focal length of the lens

• According to the question, f = 0.5 m

• R= 2 x 0.5 = 1.0 m

Convex mirror is also known as diverging mirror because it diverges the rays of light, which fall on its reflecting surface.

• All the light rays which are parallel to the principal axis of a convex mirror, appear to diverge from the principal focus (F) after reflection from the mirror.

Power is defined as the multiplied product of square of Current and Resistance.

• It is expressed as I²R, where P is the Power which. can be measured in Watt: I is the Electric Current which can be measured in Ampere: R is the Resistance which can be measured in ohm.