An object 5 cm in height is placed 15 cm away from a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a focused image? Find the height of the image.
An object 5 cm in height is placed 15 cm away from a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a focused image? Find the height of the image.
Here's the solution to the problem:
Given:
- Object height, h = 5 cm
- Object distance, u = -15 cm (negative as per sign convention)
- Focal length, f = -10 cm (negative for concave mirror)
To find:
- Image distance, v
- Image height, h'
Solution:
We can use the mirror formula to find the image distance:
1/f = 1/v + 1/u
Substituting the given values:
1/(-10) = 1/v + 1/(-15)
-1/10 = 1/v - 1/15
1/v = -1/10 + 1/15
1/v = (-3 + 2)/30
1/v = -1/30
v = -30 cm
The screen should be placed 30 cm in front of the mirror to obtain a focused image.
Now, we can use the magnification formula to find the height of the image:
Magnification, m = h'/h = -v/u
Substituting the known values:
h'/5 = -(-30)/(-15)
h'/5 = 30/-15
h'/5 = -2
h' = -10 cm
The height of the image is 10 cm. The negative sign indicates that the image is inverted.
Answer:
- The screen should be placed 30 cm away from the mirror.
- The height of the image is 10 cm. The image is inverted.
Note: These calculations follow the sign conventions used in optics.