1. A concave mirror has a focal length of 30 cm. What kind of image is produced

Question

1. A concave mirror has a focal length of 30 cm. What kind of image is produced by an object located 60 cm from the mirror? Where is it located and what is its magnification?

2. A 15-cm ruler is palced 30 cm in fornt of a concave mirror with a focal length of 20 cm. Where is the image located and how big is it?

3. A 15-cm ruler is placed 75 cm from a converging lens with a focal length of 60 cm. Where is the image located and how big is it?

4. A tourist in Yellowstone National Park takes a photograph of a buffalo that is 40 m away and 2,2m tall. If the lens has a focal of 50 mm, howl arge is the image of the buffalo on the film?

5. Upon entering material Xm light slows down by 30 percent compared to its speed in vacuum. What is the imdex of refraction of Material X?

6. What is the thinnest soap film that will strongly reflect yellow light with a wave length of 589 nm?

Please show work and explain.

Explanation / Answer

1) so 1/i + 1/o = 1/f

1/60 + 1/i = 1/30

1/i = 1/30 - 1/60 = 1/60

i = 60 cm

since i>0 real

M = -i/o = -60/30 = -2

2)

1/30 + 1/i = 1/20

1/i = 1/20 - 1/30 = 3/60 - 2/60 = 1/60

i = 60 cm

M = -i/o = -60/30 = -2

so h' = 2*15 = 30 cm

3)

1/75 + 1/i = 1/60

i=300 cm

M = -i/o = -300/75 = -4

so h' = 4*15 = 60 cm

4)

1/40 + 1/i = 1/50.0E-3
i=0.05
so M = 0.05/40
h'= 2.2*0.05/40=0.00275 m or 2.75 mm

5) v = c/n
so if slowed down by 30 percent
1/n = 0.7
n = 1/0.7 = 1.429

6)

so soap film is air to soap to air
so one low to high
so (m + 1/2) lambda/n = 2 d

d = lambda/4n = 589/(4*1.42)=103.7 nm

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