Light and Lenses

AKS 12: Optics quick review

Thicker in the middle and thinner on the ends.

Bends light together towards a focal point on the far side of the lens.

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Converging Lenses

Converging lenses produce REAL, INVERTED images that can be magnified, reduced, or the same size as the object unless the object is at F (no image) or closer than F (virtual, upright, magnified image)

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Converging Lens Images

Thinner in the middle and thicker on the ends.

Bends light away as if it comes from the focal point on the near side of the lens.

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Diverging Lenses

Diverging lenses produce VIRTUAL, UPRIGHT, REDUCED images ALWAYS!!

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Diverging Lens Images

Multiple Choice

How does a concave lens differ from a convex lens?

• A convex lens is another way to describe a plane mirror; a concave lens is curved

• A concave lens is curved inward on both sides; a convex lens is on only one side

• A convex lens has a thick center and thin edges, a concave lens has a thin center and thicker edges

• A convex lens has a thin center and thick edges. a concave lens has a thick center and thinner edges

Multiple Choice

A student is creating a model of a concave lens. The diagram shows her incomplete model. Which action would best complete her model?

• The student should draw the light moving into the lens and then exiting in converging lines.

• The student should draw the rays of light moving into the lens and then exiting at right angles.

• The student should draw the rays of light moving into the lens and then exiting in a straight path.

• The student should draw the light moving into the lens and then exiting in lines that are spreading out.

Multiple Choice

Which model shows what happens when light passes through a convex lens?

Multiple Choice

This image is...

• Inverted and smaller
• inverted and bigger
• not inverted and smaller
• not inverted and bigger

A flat mirror.
Real light rays all stay on the object side of the mirror. Image is formed by virtual light.
Angle of incidence = angle of reflection

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Plane Mirror

Always VIRTUAL, UPRIGHT, SAME SIZE as the object.
d_o=d_i

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Plane mirror images

Multiple Choice

In the figure shown, if angle i is increased, angle r will _________________.

• none of these

• decrease by the same amount

• remain the same

• increase by the same amount

Multiple Choice

If the angle of incidence in the diagram is 80°, the angle of reflection will be:

• 10°

• 100°

• 90°

• 80°

Multiple Choice

The image produced is

• real

• virtual

• magnified

• closer

d_o=object distance
d_i=image distance
f=focal length

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Thin Lens Equation

Multiple Choice

The focal length of the lens in your eye is about 0.015 m. If the object is 1 m from your eye, where is the image produced? 

• 0.0315 m
• 0.0243 m
• 0.0152 m
• 0.0601 m

Multiple Choice

A converging lens produces an image twice the size of the original. If the object is placed 0.40 m from the lens, and the image produced is 0.80 m from the lens. What is the focal length of the lens? 

• 0.351 m
• 0.267 m
• 0.416 m
• 0.112 m

M=magnification
d_o=object distance
d_i=image distance
h_o=object height
h_i=image height

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Magnification Equation

Multiple Choice

What is the magnification of a lens if the object is 4cm tall and the image has a height of 7cm?

• 1.75x

• 0.57x

• 3x

• -3x

Multiple Choice

An object placed 20cm from a lens forms an image 25cm away from the lens. What is the magnification of the lens?

• 0.8x

• 1.25x

• 5x

• 45x