Laws of reflection Law 1 The incident ray, normal and the reflected ray are all in the same plane.
Law 2 The angle of reflection (r) is equal to the angle of incidence (i ). i r i the angle of incidence, r angle of reflection
Laws of refraction Law 1 The incident ray, normal and the reflected ray are all in the same plane.
Law 2 The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for two given media.
sin i sin r n
n is the refractive index between the two media, i the angle of incidence, r angle of reflection This law is also known as ‘Snell’s Law’.
Electricity
Coulomb’s law The electrostatic force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
F r Q1Q2 d2
Q1 charge on the body 1, Q2 charge on the body 2, d distance between them
Joule’s law The rate of heat production in a conductor is proportional to the the square of the current provided its resistance is a constant.
P I2
P rate of production, I current Ohm’s law
Under constant physical conditions, the potential difference across a conductor is propor- tional to the current flowing through it.
