Measurement of the focal length of a converging lens

Label this diagram

a - light box

b - slit

c - card

d - lens

e - metre ruler

f - image distance

g - object distance

Demonstrate the method of this experiment • 1

• Move card back and forth until a sharp image of the slit is formed

Demonstrate the method of this experiment • 2

• Measure and record u and v using the metre stick

• Repeat previous steps by changing the distance

Demonstrate the method of this experiment • 3

• Calculate the focal length using the distance formula

• Calculate the average of f for each set of values

Define 2 precautions that are associated with this experiment • 1

Keep lens and card vertical

Define 2 precautions that are associated with this experiment • 2

Measure u and v from the centre of the lens

Label This Formula

The Distance Formula

v - image distance

u - object distance

f - focal length

When is u positive and negative?

U is always positive

Never negative

When is v positive and negative?

Positive - Real Images

Negative - Virtual Images

When is f positive and negative?

Positive - Converging Lens

Negative - Diverging Lens

What page of the log tables can you find the Distance formula?

60