Optics test Attempt both questions
Question 1
A student is designing a demonstration telescope with just two convex lenses. The dimensions of the cardboard tubes he wants to use are shown on the diagram which is drawn to scale (not actual size).
For your assistance a central line has been drawn on the axis of the tubes.
He has a box of short focal length convex lenses and a box of larger lenses with longer focal lengths.
a Why should he select the objective lens for this telescope from the box of longer focal length, larger lenses?
Two reasons.
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[2 marks]
b The object he wants to view is in position far to the left of the tube. An objective lens of suitable focal length is shown in position in the fixed tube. Two rays are shown coming from the object.
What is the focal length of the objective?
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c Select the focal length you now need for the eyepiece and complete the ray diagram showing the final position of the image.
[2 marks]
d What is the magnification of your telescope with your selected eyepiece?
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e Having got the first model to work, he now decides he wants to make a telescope for spying on his friends with a greater magnification of x 20.
Give advice
What lenses could he try and where should he put them? What do you suggest he does with the tube and what could he try as a better eyepiece?
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[4 marks]
Question 2
A student is designing a demonstration microscope with just two convex lenses. The dimensions of the cardboard tubes he wants to use are shown on the diagram which is drawn to scale (not actual size).
For your assistance a central line has been drawn on the axis of the tubes.
He has a box of short focal length convex lenses and a box of larger lenses with longer focal lengths.
a From which box should he select the objective lens for this microscope?
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[1 mark]
b The object he wants to magnify is in position to the left of the objective. The focal length of the objective is 5.0 cm.
Draw the ray diagram to locate the real image inside the microscope.
[1 mark]
c The focal length of the eyepiece is 10 cm. Complete the ray diagram showing the final position of the image.
[2 marks]
d What is the magnification of your microscope?
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[1 mark]
e Why - when using a microscope does the image travel in the opposite direction to the movement of the object?
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[1 mark]
f The image quality in the demonstration microscope is poor because of spherical and chromatic aberrations.
What do these aberrations look like and how can they be reduced?
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[3 marks]