JSS3 Second Term Basic Science Lesson Note – Light Energy

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WEEK TWO

TOPIC:   LIGHT ENERGY

CONTENT:

• Review of the concepts of (I) reflection (ii) refraction of light
• Apparent depth and its dangers to swimmers.
• Vision
• Dispersion and rainbow.

Light is a form of energy. It enables us to see things when it is reflected from objects into

our eyes. Objects that give light by themselves are called luminous objects. E.g sun, while those that cannot give light but only reflect light from luminous objects are called non-luminous objects. E.g moon.

Reflection of light

Reflection is the sending back of rays of light after striking a reflecting surface. Reflection from a surface depends on how smooth or rough the surface is. A reflection from a smooth surface like a mirror is regular while that from rough surfaces like walls and stones is irregular or diffuse.

Light Rays

Light ray is the pathway through which light travels.  Light ray could be incident (ray from the light source) and reflected ray (ray from the reflected object). When rays are many they form beam. A beam is the collection of more than one ray. A beam could be convergent (rays meeting at a point), divergent (rays going out from a point) and parallel (rays moving in a straight line).  A substance that allows light to pass through it so that the object is seen clearly is called transparent object. Objects that does not allow light pass through it is called opaque object and those objects that allow light pass through it but the objects are not seen clearly is known as translucent objects.

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