Read the following passage and answer the questions below - Leaving Cert Physics - Question 11 - 2019
Question 11
Read the following passage and answer the questions below.
One of the most common sights anywhere in the world are eyeglasses. Since we depend so much on the lenses... show full transcript
Worked Solution & Example Answer:Read the following passage and answer the questions below - Leaving Cert Physics - Question 11 - 2019
Step 1
a) Name the part of the eye where an image is formed.
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Answer
The part of the eye where an image is formed is the retina.
Step 2
b) What is the function of the pupil?
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Answer
The pupil controls the amount of light that enters the eye by adjusting its size.
Step 3
c) The eye can focus light from both nearby and distant objects. Describe how the eye allows this effect to happen.
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The eye accommodates by adjusting the shape of the lens via the ciliary muscles. When viewing distant objects, the lens flattens, reducing its curvature. Conversely, when viewing nearby objects, the lens becomes more rounded to increase its optical power.
Step 4
d) Name two of the most common eye defects.
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The two most common eye defects are myopia (short-sightedness) and hyperopia (long-sightedness).
Step 5
e) What type of lens corrects short sightedness? Draw a sketch of this lens.
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A diverging lens corrects short sightedness.
The sketch above shows a diverging lens and the light rays diverging from it.
Step 6
f) Copy the diagram below into your answerbook and complete the ray diagram to form a real image.
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To complete the ray diagram:
Draw two incident rays from the object.
Extend the rays to meet at a point on the opposite side of the lens to represent the real image formed.
Step 7
g) The power required to clearly view a nearby object is 38 m⁻¹. A person with an eye defect has a maximum power of 32 m⁻¹. Calculate the power of the lens required to correct this defect? What is the focal length of this lens?
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Power of the lens required: 38 m⁻¹ - 32 m⁻¹ = 6 m⁻¹.
To calculate the focal length (f):
P=f1
Thus, f=P1=61=0.167 m=16.7extcm
Step 8
h) Light undergoes refraction as it passes through a lens. What is meant by refraction?
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Refraction is the bending of light rays as they pass from one medium to another due to a change in their speed. This bending allows the lens to focus light onto the retina.
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