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Perform this activity.
Be blindfolded. Let someone place an item between 15 metres to 20 metres away from you. Now search for the item. Record the time you found the item. Now, be blindfolded again. Let someone place the item somewhere else but within the same distance as before. Take off your blindfold. Search for the item. Record the time you found the item.
Click on the link provided above and do the exercise on the functions of the parts of the eye. When complete check your answer. The system will then mark your work. Print and paste your work.
3
How does a lens work? Complete the sentence below using the words from the box.
We have a lens in each of our _______________. This is a ______________ lens. The job of this lens is to ______________ the ________________ so we can_____________________. The point at which the rays cross is called the focus or the ____________________. The light is ________________________as it goes into the and as it comes back out.
eyes
refracted
light
focal point
focus
see
convex
4
Watch video:
4a
Below are the steps in how humans see. Arrange them in a chronological order by putting numbers (1, 2, 3, 4, 5, 6) in the “position” column to reflect the right order in which they should be.
Position
Steps
When you look at an object, light reflected from the object goes through the pupil of your eye.
Your brain sorts the image out so you see it the right way round.
The cornea and the lens focus the light onto the retina.
An inverted image is formed on the retina. The retina is made of light sensitive cells called photoreceptors.
The iris, a muscle that controls the size of the pupil, allows the correct amount of light to enter your eye.
When the image forms on the photoreceptors in the retina, chemical reactions produce and electrical impulse that travels up the optic nerve to your brain.
4b
Fill in the blank: A medical doctor who specialises in examining, diagnosing, and treating eyes and eye diseases is called a/an ____________________.
4c
Visual acuity test, visual field test and tonometry test are tests that an ophthalmologist performs on the eye. Match the name of the term to its meaning:
Visual acuity test
?????
A person reads an eye chart to measure how well he or she sees at various distances.
Visual field test
?????
This test determines the fluid pressure inside the eye to evaluate for glaucoma.
Tonometry test
?????
Ophthalmologists use this test to measure side, or peripheral, vision.
4d
What are the roles of:
i
Rods
ii
Cones
5
How does the eyesight of humans compare with other creatures? Compare with any three of the following animals: eagles, owls, mantis shrimp, deer, goat, horse, elk, sheep, goat.
6
Complete the following:
6a
Compare the key features of the eye and a camera by finishing the table.
Feature in a camera
Feature in an eye
Use
Pupil
Lens
Shutter
Retina
Receives light
6b
Write a paragraph below to compare how the eye and the camera work. Cover the following factors in your answer:
i
Similarities: What features do they have in common? What does each convert the light energy into when it is processed? Which way up does the image form in both?
ii
Differences: How does the lens change in each to produce an image? How do the types of image made by each compare? How are the images captured and kept?
7
With reference to the eye chart explain:
7a
20/20 vision
7b
20/70 vision
8
What is visual impairment?
9
Define these eye problems and state their "cures".
________________ is the bending of light when it passes through a transparent medium such as glass, lens or water.
10b
The refractive errors are _______________, ___________________, ____________ and _______________.
10c
_________________is also known as near-sightedness. People with this have eyes that are a little longer than normal, measuring from the front of the eyeball to the back. Therefore, light focuses in front of the retina instead of on it.
10d
___________________ is also known as farsightedness. People with this have trouble focusing on things close up because their eyes are too "short" from front to back. Therefore, light focuses behind the retina instead of on it, causing blurry vision.
10e
_____________________ is a condition in which your eye isn’t completely round. Therefore, light gets bent more in one direction than another. That means only part of an object is in focus so things at a distance may look blurry and wavy.
10f
_________________ is the normal loss of near focusing ability that occurs with age. Most people begin to notice the effects of presbyopia sometime after age 40, when they start having trouble seeing small print clearly.
10g
Read Genesis 48:10. Which of the refractive errors did Israel have?
Now the eyes of Israel were dim with age, so that he could not see. Then Joseph brought them near him, and he kissed them and embraced them. — Genesis 48:10 (NKJV)
10h
State if the following statement below is true or false: “All the refractive errors can be corrected by wearing the right glasses or contact lens.”
11
Eye care:
11a
How should I clean my eyes?
11b
Write one sentence on how we can strain our eyes.
11c
How should we rest them?
11d
Matthew has been using a computer continuously for 4 hours! Now he is complaining of eye strain. Give Matthew three pieces of advice to help him relax his eyes.
11e
Explain the 20-20-20 rule of eye relaxation.
11f
What do I do if I cannot see very well?
12
Give two meanings to the expression “The eyes are a window to the soul.”
13
What are the effects of exposing ourselves to watching:
13a
Violence/pornography (mention three)
13b
Video games: Give three advantages and disadvantages
13c
Social media: Give three advantages and disadvantages
14
Explain 1 Samuel 16:7.
But the Lord said to Samuel, “Do not look at his appearance or at his physical stature, because I have refused him. For the Lord does not see as man sees; for man looks at the outward appearance, but the Lord looks at the heart.” — 1 Samuel 16:7 (NKJV)
15
Explain “fixing our eyes on Jesus.” (Hebrews 12:2)
looking unto Jesus, the author and finisher of our faith, who for the joy that was set before Him endured the cross, despising the shame, and has sat down at the right hand of the throne of God. — Hebrews 12:2 (NKJV)
16
Mention four ways that life can be made easier for the visually impaired.
17
Optical illusion:
17a
Fill in the blanks using the word bank in the box below the passage.
_____________ Illusions can use colour, ______________ and patterns to create ___________ that can be deceptive or misleading to our _____________. The information gathered by the eye is processed by the brain, creating a perception that in reality, does not match the true image. Perception refers to the interpretation of what we take in through our _____________. Optical illusions occur because our brain is trying to _______________ what we see and make sense of the world around us. Optical illusions simply trick our brains into seeing things which may or may not be _____________.
images
eyes
brains
optical
real
light
interpret
17b
Provide the answers to the optical illusions below.
Hermann Grid Illusion
How many black dots are in this image?
Rotating Snakes Illusion
Are the circles moving in the image?
Café Wall Illusion
Are the horizontal lines sloping or straight?
Müller-Lyer Illusion
Take a very close look at the 2 line segments. Do you think one line is longer than the other?
Lightbulb Illusion
Stare closely at this lightbulb for 25 seconds. Then immediately stare at a white wall or sheet of paper. What do you see?
