Answer :
Answer:
Explanation:
22. To find the focal length of a concave mirror approximately, you can use the mirror formula: \[ \frac{1}{f} = \frac{1}{u} + \frac{1}{v} \] where \( f \) is the focal length, \( u \) is the object distance, and \( v \) is the image distance. By placing an object at a known distance from the concave mirror and observing the position of its image, you can estimate the focal length.
23. A concave mirror is used in a solar furnace. This type of mirror is chosen because it can converge sunlight to a focal point, resulting in high temperatures at that point. This is useful for various industrial applications, such as melting metals or generating steam.
24. Dentists use concave mirrors known as dental mirrors. These mirrors are used to reflect light into hard-to-see areas of the mouth, allowing dentists to examine teeth and gums more easily during dental procedures.
25. Concave mirrors are used as shaving mirrors because they produce virtual, upright, and magnified images of the face. This makes it easier to see details while shaving, such as individual hairs and contours of the face, leading to a smoother and more precise shave.
26. Two uses of concave mirrors are:
- Reflecting telescopes: Concave mirrors are used as the primary mirrors in reflecting telescopes due to their ability to gather and focus light, producing clear and detailed images of distant objects.
- Headlights: Concave mirrors are used in headlights of automobiles to produce a parallel beam of light, which increases visibility for drivers at night. This is achieved by focusing the light from the bulb into a beam that travels forward.
Concave mirrors are chosen for these uses because they can converge light rays to a focal point, resulting in clear and focused images. Additionally, their ability to magnify objects makes them suitable for applications where detailed observation is required.
Long Answer Type Questions
27. (a)
(i) When the object is placed between the pole and the focus of a concave mirror:
In this case, the image formed is virtual, erect, and magnified. It is located behind the mirror and is larger than the object.
(ii) When the object is placed between the centre of curvature and the focus of a concave mirror:
The image formed is real, inverted, and magnified. It is located beyond the centre of curvature and is larger than the object.
(b) One use of concave mirrors based on the formation of an image as in case (i) above is in makeup mirrors. The magnified image produced by the concave mirror helps in applying makeup with precision.
28. (a) Two circumstances in which a concave mirror can form a magnified image of an object are:
- When the object is placed between the focus and the pole of the mirror.
- When the object is placed beyond the centre of curvature of the mirror.
(b) The circumstance in which a concave mirror forms a magnified image when the object is placed between the focus and the pole enables it to be used as a shaving mirror. This is because the magnified image allows for a closer examination of facial hair, making it easier to shave with precision.