Light waves

Light waves travel in straight lines as transverse waves. The vibrations in transverse light waves travel at a perpendicular (90° angle) to the direction that light travels.

Visible light is the light we detect with our eyes. We can see an object when light reflects off an object and into our eyes. As you can see in the diagram below.

In order to see the leaves, light is reflected off the leaves, into our eye.

Light is able to travel through space (which is a vacuum) because, unlike sound, light does not need particles to travel.

Objects Transmitting Light

Light can also travel through gases, liquids and some solids. When light can pass through objects, we say the objects can transmit light. Transparent, translucent and opaque are terms we use to describe how objects transmit light. Objects that transmit light (which means to let light through) are either transparent or translucent and objects that can not transmit light are called opaque objects.

Transparent objects

Transparent is the word used to describe something that is clear or see through. If an object is transparent, you can see a clear image through the object. An example of this is a glass window.

As glass is transparent (see through), it transmits light.

Most of the light that hits the glass passes through, which is why you can see a clear image through the glass window. However, some light gets reflected, which is why you can often see a clear reflection through glass.

Translucent objects

Translucent is a word used to describe something that transmits light but does not allow you to see a clear image through it.

For example, frosted glass is a translucent object.

Some of the light that hits the glass passes through but the light that is transmitted gets scattered, which is why you can only see fuzzy images through frosted glass.

The remaining glass that hits the light is reflected and the reflected light is also scattered, so the reflection is not clear either.

Opaque objects

The word opaque is used to describe an object in which light is not capable of passing through.

Opaque objects are objects which do not transmit light. Most of the light that hits opaque objects is absorbed, however, some light is reflected.

Any object you can’t see through is an opaque object.

Speed of Light

The speed of light is around 300,000,000 m/s, which is much faster than the speed of sound. This means it takes light just over 8 minutes to get to Earth.

This explains why you see lightning before you hear it. Although the light and sound are produced at the same time, the light reaches your eyes before you are able to hear the sound.

Luminous and Non-Luminous Objects

Objects which emit (give out) light are called luminous objects. Examples of luminous objects are:

  • Sun
  • Stars
  • Electric bulbs
  • Candles

Objects that do not emit light are called non-luminous objects. Most objects are non-luminous. We are able to see non-luminous objects when light reflects off them, into our eyes.