An object is placed at a distance of 15 cm from a concave lens of focal length 30 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.
CBSE OUTSIDE DELHI - SET 3 2017
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Given, u = -15cm (It is to the left of the lens) f = -30 cm (It is a concave lens) Using the lens formula $\frac{1}{\text{f}}=\frac{1}{\text{v}}-\frac{1}{\text{u}}$$\Rightarrow \frac{1}{\text{v}}=\frac{1}{\text{f}}+\frac{1}{\text{u}} =\frac{1}{(-30)} + \frac{1}{(-15)}$
$\therefore \frac{1}{\text{v}}=-\frac{3}{30}=-\frac{1}{10}$
$\therefore \text{v}=-10\text{cm}$
The negative sign of the image distance shows that the image is fromed on the left side of the concave mirror. Thus, the image formed by a mirror is virtual, erect and on the same side as the object.
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An object 1cm tall is placed 30cm in front of a convex mirror of focal length 20cm. Find the size and position of the image formed by the convex mirror.
Draw a ray diagram to show the formation of a real diminished image of an object by a convex lens. In your diagram, the position of object and image with respect to the principal focus should be shown clearly.
Redraw the following diagram on your answer-sheet and show the path of the reflected ray. Also mark the angle of incidence $(\angle\text{i})$ and the angle of reflection $(\angle\text{r})$ on the diagram.
“A concave mirror of focal length ‘f’ can form a magnified erect as well as an inverted image of an object placed in front of it.” Justify this statement stating the position of the object with respect to the mirror in each case for obtaining these images.