Light Refraction & Reflection PDF

LIGHT Refraction As the light leaves the water, the direction it is travelling In changes. This is called refraction Refraction happens whenever light travels from one medium (material) to another. A) State the difference between reflection and refraction: Reflection is the bouncing back of li...

LIGHT Refraction As the light leaves the water, the direction it is travelling In changes. This is called refraction Refraction happens whenever light travels from one medium (material) to another. A) State the difference between reflection and refraction: Reflection is the bouncing back of light when it strikes a smooth surface. Refraction is the bending of light rays when it travels from one medium to another. What does a lens do? There are two lenses in your body: The lens in each of your eyes is a convex or converging lens. The point where the rays cross is called the focus or focal point. B) Describe what a lens does to light: It focuses the light and enables you to see. The light is refracted as it goes into the lens and as it comes back out. The eye and the camera How do you see?  When you look at an apple, light reflects off the apple into your eye. The light enters your eye through the pupil. The lens and the cornea focus the light onto the retina. The light forms a real image. A chemical reaction produced an electrical signal that is sent drown your optic nerve to your brain. A) State which parts of the eye focus the light: Cornea (the transparent outer part of your eye) and the lens focus the light onto the retina. What happens in the retina? Retina is a photosensitive material that contains cells that respond to light. Called photoreceptors Two types of photoreceptor: Rods-sensitive to movement and dim light Cones-sensitive to bright light and colour B) State the type of reaction that takes place in the retina Chemical reactions How is the eye like a camera? A camera produces an image, just like your eye. One of the simplest cameras is a pinhole camera. Light enter the camera through the pinhole, just like it does through your pupil. An image is formed on the screen, just like it is on your retina. At the back of a digital camera there is a grid of photosensitive picture elements, or pixels. This is called a charge-coupled device (CCD). The light produces an electrical, not chemical, effect. C) Name the photosensitive grid at the back of a digital camera Charged-coupled device (CCD) Colour Splitting white light White light is made up of seven different colour of light, use a prism to split white light into a spectrum. This is called dispersion. The spectrum of white light is continuous. Sir Isaac Newton first did this experiment in about 1666. Dispersion happens because different colours of light are refracted by different amounts. Light with a higher frequency is refracted more than light with a lower frequency. A) State what a prism does to light When white light is passed through a glass prism it splits into it’s spectrum of colours in order. Adding colours Primary colours of light: red,blue,and green Secondary colours of light: cyan,yellow,and magenta When you mix two primary colours you get secondary colours of light. You get white light when you mix all three colours of light. What do filters do to light? Filters transmit the colours that they are and absorb the rest. Why are objects different colours? Black objets absorb all the colours of light and white objects reflect all the colours of the light.