How We See.

How We See

How do you see an object? Light from the object enters your eye.
(L4) Describe how light travels from luminous sources. (L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects. How do you see an object? Light from the object enters your eye. Do you see all objects in the same way? There are two ways you see objects: You see some objects because they are light sources. You see other objects by reflected light.

Light travels in a straight line directly into your eye.
(L4) Describe how light travels from luminous sources. (L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects. A luminous object gives out light and can also be called a light source. How does light from a light bulb and other light sources reach your eye? Light travels in a straight line directly into your eye.

Objects that do not give out light are non-luminous.
(L4) Describe how light travels from luminous sources. (L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects. Objects that do not give out light are non-luminous. How does your eye see non-luminous objects such as a book? Light from the light source strikes the book and some of the light is reflected into your eye.

(L4) Describe how light travels from luminous sources.
(L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects. Why does the boat see the light from the light house before hearing the fog horn?

Luminous Source Worksheet
(L4) Describe how light travels from luminous sources. (L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects. Luminous Source Worksheet Circle the luminous sources Label the luminous sources Draw how the one-armed man would be able to watch television. Draw how the man would be able to see the chair.

(L4) Describe how light travels from luminous sources.
(L5) Explain how we see both luminous and non-luminous light sources. (L6) Use ray diagrams to show how we see both luminous and non-luminous objects.

Transparent – these are materials which let all of the light straight through.
Translucent – these materials let light through but it is randomly scattered. Opaque – these materials let no light through.

translucent transparent opaque
Leave some space under each one to draw something! Fill in the gaps in the sentences below: An object that allows all light to pass through it is called……………………………………………… An object that allows just some light to pass through it is called………………………………… An object that allows no light to pass through it is called……………………………………………… translucent transparent opaque

Why do you shadows form?

The Eye starter Label your diagram of the eye in as much detail as possible Extension questions Why do you think the outside layer of the eye (the sclera) is white? Why do you think the inside layer of the eye (the choroid) is black? Hint: think about how light reflects from different surfaces

Suspensory ligaments

Did you notice the small grayish dots between the black boxes
Did you notice the small grayish dots between the black boxes. They are not part of the drawing - they were put there by your brain! Scientists call this "visual vibration." Basically it means that when you see patterns of black and white, your eye sometimes confuses the two and blends them into patterns of gray that you see here. You are seeing something that is not really there!

Hold a pen in one hand away from your face
Depth Perception Task 2 Close one eye Hold a pen in one hand away from your face Try to touch the end of the pen with your other hand - KEEP one eye closed. Repeat with both eyes open Is your perception of depth better with monocular vision or binocular vision?

Look into your partner eyes and observe the size of the pupil.
The pupil reflex Task 1 Look into your partner eyes and observe the size of the pupil. Cover one of your eyes with your hand for about 10 seconds and then take your hand off. Observe the pupil. What do you notice? What type of reaction is this? Why is this a very useful reaction

Now focus on the classroom clock for 30 secs
Accommodation Task 4 Hold your finger about an inch from the tip of your nose and try to focus on it for 30 secs Now focus on the classroom clock for 30 secs Now answer these questions: Which is more difficult? Which situation is your body doing more work? Do you therefore think looking at near objects involves the muscles in your eyes contracting or relaxing. Explain your answer. Explain what is happening when you are looking at the clock

1 Which of these statements is true?
A Light travels in straight lines. B Light is stopped when it meets a solid object. C Light does not travel in straight lines. D Light will only travel for about 2000km before it stops.

2 Which of these is not a source of light?
A a light bulb B the Sun C a mirror D a TV

3 Shadows are formed because:
A light will only travel a certain distance before it stops. B a substance called ‘darkness’ collects behind some objects. C some objects do not give out light in all directions. D light cannot go through some objects.

4 Which statement is true?
A Sound travels faster than light. B Sound will not travel. Only light can travel. C Light travels faster than sound. D Light and sound travel at the same speed.

5 Objects that light can easily pass through are said to be:
A transparent. B apparent. C opaque. D oblong.

6. Which phrase best completes the following sentence
6 Which phrase best completes the following sentence? We see things because: A they are luminous. B the Sun shines on them. C light from them enters our eyes. D light from our eyes shines on them.

7 Opaque objects can: A transmit and reflect light. B transmit and absorb light. C reflect and absorb light. D only reflect light.

8 Which of these will absorb the most light?
A a white sheet of paper B a sheet of clear glass C a black piece of card D an orange piece of card

9. Which of these diagrams show how light rays. travel
9. Which of these diagrams show how light rays travel?... There may be more than one that is right!

ANSWERS Swap your books to mark each other’s answers
ANSWERS Swap your books to mark each other’s answers. Write in pen and put your initials