PLEASE HELP!!! (Physics 11)?

2020-07-24 10:24 pm

1. A glue stick that is 11.00 cm tall is placed 15.0 cm in front of a convex mirror that has a focal length of 4.5 cm. What are the characteristics of the image? Use formulae to determine.
2. You put a 3.00cm candle 10.0 cm in front of a convex lens. If the lens has a focal length of 7.5 cm, what is the a) the distance of the image from the lens?b) The size of the image? c) The characteristics of the image? 3. A 4 cm high object is placed at a distance of 1.75 f (focal length) from a convex lens with a focal length of 2.0 cm. What are the characteristics of the image? 4. A 3.00cm candle is placed 9.0 cm in front of a concave lens. If the lens has a focallength of 4.0 cm, what is (are) a) the distance of the image from the lens? b) The size of the image?c) The characteristics of the image?5. In this question, the candle that is being used is only 2.0 cm tall and you are asked to place it 5.0 cm infront of a lens. The virtual image produced is 4.0 cm tall. What is the focal length of the lens? What type of lens was used to produce these results?

回答 (1)

micatkie

2020-07-24 11:01 pm

✔ 最佳答案

1.
(1/u) + (1/v) = 1/f
(1/15) + (1/v) = -1/4.5
1/v = -(1/4.5) - (1/15)
1/v <0 and thus v < 0
Hence, the image is virtual and upright.

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2.
a)
(1/u) + (1/v) = 1/f
(1/10.0) + (1/v) = 1/7.5
1/v = (1/7.5) - (1/10.0)
v = 1 / [(1/7.5) - (1/10.0)]
v = 30.0
Distance of the image from the lens = 30 cm

b)
Size of the image
= 3.00 × |v/u| cm
= 3.00 × |30.0/10.0| cm
= 9.00 cm

c)
As v > 0, the image is real and inverted.

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3.
Object distance = 1.75 × 2.0 = 3.5 cm
(1/u) + (1/v) = 1/f
(1/3.5) + (1/v) = 1/2.0
1/v = (1/2.0) - (1/3.5)
1/v = 0.21 > 0
v > 0
The image is real and inverted.

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4.
a)
(1/u) + (1/v) = 1/f
(1/9.0) + (1/v) = -1/4.0
1/v = -(1/4.0) - (1/9.0)
1/v = 1 / [-(1/4.0) - (1/9.0)]
v = -2.8
Distance of the image from the lens = 2.8 cm

b)
Size of the image
= 3.00 × |v/u| cm
= 3.00 × |-2.8/9.0| cm
= 0.93 cm

c)
As v < 0, the image is virtual and upright.

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5.
v = -5.0 × (4/2) = -10

(1/u) + (1/v) = 1/f
(1/5) - (1/10) = 1/f
1/f = 0.1
f = 10
Focal length of the lens = 10 cm

As f > 0, it is a convex lens.

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