Question

The focal length of a converging lens is 20 cm. The image of the object placed 60 cm from the centre of this lens is real and __________________

Answer 1

Answer on Question #60009-Physics-Optics

The focal length of a converging lens is 20 cm. The image of the object placed 60 cm from the centre of this lens is real and _______________.

Answer: inverted.

$$u = 60 \text{ cm}, f = 20 \text{ cm}.$$ $$\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{20} - \frac{1}{60} = \frac{1}{30}$$ $$v = 30 \text{ cm}$$

The image is real and is formed on the other side of the lens. The magnification is

$$m = - \frac{30}{60} = - \frac{1}{2}.$$

The negative sign tells us that the image is inverted.

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