Optical device Object distance Focal length Height of object (cm) (cm) (cm) Convex lens 20 10 6 Concave mirror 30 10 6…

For Convex lens
• Position:
$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$ (1 Mark)
$\frac{1}{v} = \frac{1}{f} + \frac{1}{u}$ (1 Mark)
$\frac{1}{v} = \frac{1}{10} + \frac{1}{-20}$ (1 Mark)
$v = +20cm$ (1 Mark)
• Nature: real, inverted (½ Mark)
For Concave mirror
• Position:
$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$ (1 Mark)
$\frac{1}{v} = \frac{1}{f} - \frac{1}{u}$ (1 Mark)
$\frac{1}{v} = \frac{1}{-10} - \frac{1}{-30}$ (1 Mark)
$v = -15cm$ (1 Mark)
• Nature: real, inverted (½ Mark)
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Alternate answer
Convex lens: -
• When object is placed at centre of curvature, the image is formed at centre of curvature. (1 Mark)
• Nature of image is real and inverted. (½ Mark)
Concave Mirror: -
• When object is between infinity and centre of curvature the image is formed between focus and centre of curvature. (1 Mark)
• Nature of image is real and inverted. (½ Mark)