Free Printable 8.04: Lenses: Power of a Lens

1.

The power of a lens is positive for a ...

a)

Concave (Diverging) Lens

b)

Convex (Converging) Lens

2.

The power of a lens is negative for a ...

a)

Convex (Diverging) Lens

b)

Concave (Converging) Lens

3.

The formula for the power of a lens is...

a)

$P\ =\ 1\ +\ f$

b)

$P\ =\ 1\ -\ f$

c)

$P\ =\ \frac{1}{f}$

d)

$P\ =\ \frac{1}{1\ +\ f}$

4.

Calculate the power of a convex (converging) lens of focal length 40 cm

a)

+ 2.5 m^-1

b)

- 2.5 m^-1

c)

+ 2.5 cm^-1

d)

- 2.5 cm^-1

5.

Calculate the power of a concave lens of focal length 60 cm

a)

$-1.67\ m^{-1}$

b)

$+1.67\ m^{-1}$

c)

$-1.67\ cm^{-1}$

d)

$+\ 1.67\ cm^{-1}$

6.

A lens has a power of 12 m^-1. Calculate its focal length

a)

8.33 cm

b)

12.45 cm

c)

0.8 m

d)

7.5 cm

7.

A diverging lens has a power of

-\ 0.025\ m^{-1}

. Calculate its focal length.

a)

4 m

b)

40 m

c)

0.4 m

d)

40 cm

8.

Two convex lenses of power $6\ m^{-1}$ and $10\ m^{-1}$ are placed in contact. Calculate the combined power and the focal length of the combination.

a)

$P\ =16\ m^{-1}\ ,\ f\ =\ 6.25\ cm$

b)

$P\ =\ -\ 16\ m^{-1}\ ,\ f\ =\ 6.25\ cm$

c)

$P\ =\ 6\ m^{-1}\ ,\ f\ =\ 0.6\ cm$

d)

$P\ =\ -6\ m^{-1\ },\ f\ =\ 6\ cm$

9.

A concave (diverging) lens of power $-0.02\ m^{-1}$ and a convex (converging) lens of power $0.05\ m^{-1}$ are placed in contact. Find the power of the combination of the lenses. Does the combination behave as a convex or concave lens?

a)

$P\ =\ 0.03\ m^{-1}$

b)

$P\ =\ -0.03\ m^{-1}$

c)

$P\ =\ 3\ m^{-1}$

d)

$P\ =\ -\ 3\ m^{-1}$

10.

A combination of two convex lenses has a focal length of 20 cm. If the focal length of one of the lenses is 60 cm, what is the focal length of the other?

a)

30 cm

b)

40 cm

c)

20 cm

d)

60 cm

8.04: Lenses: Power of a Lens

Total questions: 10

Worksheet time: 5mins

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