Light

The Power of a Lens The power of a lens is defined as the reciprocal of the focal length in unit meter.(Important Note: f is in meter} The unit of power is diopter (D). The relationship of the power with the thickness and types of lens are shown in the diagram below. Lens Power of … Read more

Lenses There are 2 types of lenses, namely the Convex lens Concave lens Convex lenses are thickest through the middle, concave lenses are thickest around the edge, but several variations on these basic shapes are possible, as shown in figure 1.  Light rays passing through a convex or converging lens are bent towards the principal … Read more

Mirage The occurrence of mirage can be explained as follows. The air on the road surface consists of many layers. On a hot day, the air near the ground has a low specific heat capacity, hence the temperature increase faster. The hot air becomes less dense than the cold air higher up. A ray of … Read more

Total Internal Reflection and the Critical Angle In figure (a) above, the light ray is refracted away from the normal when moving from denser medium to less dense medium. Figure (b) shows that, at a specific angle, the light ray is refracted 90o from the normal. It is refracted so much that it is only … Read more

Bending of Object in a Glass A straw in a glass with water looks bended or broken. This is due to refraction of light Shallower Swimming Pool A swimming pool appears shallower than it actual is. This is because the light from the pool is refracted away from the normal when moving from water to … Read more

Refractive index The value of  sini/sinr is called the refractive index of the medium and it gives you an indication of its light-bending ability.  In SPM, when we say “refractive index”, what we mean is the absolute refractive index of a substance. The absolute refractive index of a substance is the refractive index where light … Read more

The laws of refraction The incident and refracted rays are on opposite sides of the normal at the point of incidence, and all three lie in the same plane. The value of sini sinr is constant for light passing from one given medium into another. This is known as Snell’s law. Snell’s law states that … Read more

Refraction of Light Refraction is the bending of a light ray at the boundary of two medium as the light ray propagates from a medium to another with difference optical density. Light rays are bent when they pass at an angle in or out of materials such as glass and water. The effect is called … Read more

Rules in Drawing Ray Diagram Rule No. 1The ray of light through C will be reflected back through C. Rule No. 2The ray of light parallel to the principal axis will be reflected through F. Rule No. 3The ray of light through F will be reflected parallel to the principal axis. Recommended Videos SPM Physics-Drawing … Read more

Curved Mirror A curve is part of a circle. Therefore the centre of the circle will also be the centre of the curve and is called the centre of curvature, and the radius of the circle will be equal to the radius of the curve, called the curvature radius. Important Terms All rays parallel to … Read more