Light

• What is light?

  Light is a form of energy, it is a type of electromagnetic radiation that allows the human eye to see or makes objects visible.
• You can demonstrate that light travels in straight lines using holes cut in card. You line up the holes so that light can travel in a straight line from the candle to your eye.

  You cannot see the candle unless all three holes are exactly lined up.
• How can you use light travelling in straight lines to explain the formation of shadows and other phenomena?

  When light travels, it moves in straight lines. Shadows form when an object blocks the path of light, creating an area where light cannot reach. Other phenomena like reflection and refraction occur because light changes direction when it encounters different materials, but it still follows the principle of travelling in straight lines.
• How does the eye work?

  It works like a camera. Light enters through the cornea, passes through the pupil, and focuses on the retina at the back of the eye, forming an inverted image. The retina has cells called rods and cones that convert light into electrical signals, which are then sent to the brain via the optic nerve for interpretation.
• How does the camera work?

  If you take a picture of your friend with a camera, light is reflected from your friend and goes into the camera. Your friend is the object, and an image is formed at the back of the camera. The image is focused by the lens and inverted, just as it is in your eyes.
• Light sources emit (gives out).

  Detectors absorb (take in) light.
• Emit: gives out

  Reflect: bounces back

  Absorb: take in

  Luminous: an objects emits light

  Non- luminous: an abject that doesn't emit light
• Light can be transmitted (passed through) objects it hits, or be reflected (turned back), or it can be absorbed.

  Light that is absorbed is neither transmitted nor reflected. It stays inside the object. Energy cannot disappear, so the energy of the light is transferred into thermal energy. Absorbing light makes the object heat up a bit.
• Describe the reflection at plane surface and use the law of reflection and the image formed is virtual and laterally inverted.

  When light hits a flat surface, it reflects according to the law of reflection: the angle of incidence equals the angle of reflection. This creates a virtual image that is laterally inverted, meaning it appears flipped horizontally compared to the original object.
• Reflection is the bouncing back of light when it hits a surface, like a mirror or water.
• Refraction is the bending of light when it passes from one transparent substance into another, like from air to water or glass.
• If light goes from a less dense medium to a more dense medium, like from air to water, the direction of the ray will move towards the normal.

  If the light goes from a more dense medium to a less dense medium, like from water to air, then it will move away from the normal
• Dispersion is the splitting of light into its component colors when it passes through a medium like a prism, due to each color bending by a different amount.
• When white light passes through a prism, it splits into its component colors because each color bends by a different amount. This separation is called dispersion. The colours are typically ordered as red, orange, yellow, green, blue, indigo, and violet, forming the acronym ROYGBIV.

  Different colours of light are slowed down by different amounts. Red light is slowed down the least, so it is refracted the least. Yellow light is refracted more than red, and so on. Violet light is refracted the most, so it travels the slowest in glass.
• All the colours are called a spectrum
• Explain colour addition and subtraction, and the absorption and reflection of coloured light.

  Color addition is when different colored lights combine to create new colors, like mixing red and green to make yellow. Color subtraction happens when colored filters or pigments absorb certain colors, allowing only certain colors to pass through or be reflected. Absorption occurs when an object absorbs certain colors of light and reflects or transmits others, while reflection is when light bounces off a surface without being absorbed.
• Shadows form when an object blocks the path of light, creating an area where light cannot reach. Other phenomena like refraction and reflection occur because light changes direction when it encounters different materials, but it still follows the principle of light travelling in straight lines.