The light source is 0.27 m from the lens. The screen is moved to a distance of 0.11 m from the centre of the lens so an image of the light source is seen at the screen.Calculate the focal length of the lens. Express answer to three decimal places,use SI units.
Question
The light source is 0.27 m from the lens. The screen is moved to a distance of 0.11 m from the centre of the lens so an image of the light source is seen at the screen.Calculate the focal length of the lens. Express answer to three decimal places,use SI units.
Solution
To calculate the focal length of the lens, we can use the lens formula:
1/f = 1/v - 1/u
where: f is the focal length of the lens, v is the image distance, and u is the object distance.
From the problem, we know that: u = 0.27 m (the distance from the light source to the lens), and v = -0.11 m (the distance from the lens to the screen, it's negative because the image is on the same side as the light source).
Substituting these values into the lens formula gives:
1/f = 1/(-0.11 m) - 1/(0.27 m)
Solving this equation for f gives:
f = 1 / [(1/-0.11) - (1/0.27)]
After calculating the above expression, we get:
f = -0.175 m
So, the focal length of the lens is -0.175 m. The negative sign indicates that the lens is a diverging lens.
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