1) The primary lens of a refracting telescope is 20cm in diameter and has a foca

Question

1) The primary lens of a refracting telescope is 20cm in diameter and has a focal length of 1m. If the telescope is pointed at a bird 20cm long and 20m away, Find A) The location of the birrd's image? B) the size of the bird's image? C) Is it real/virtual?, erect/inverted?, enlarged/reduced?, normal/perverted?

2)The left end of a long glass rod 4cm in diameter is polished to a convex surface of radius 10cm. The index of refraction of the glass is 1.50. An object 2cm tall is located 20cm to the left of the rod along its axis. Find: A) The location of the image B) Size of the image? C) Is the image inside or outdside the rod? real/virtual? erect/inverted? enlarged/reduced?

Explanation / Answer

1)

A)

1/s1 + 1/s1' = 1/f1

1/20 + 1/s1' = 1/1

s1' = 1.05 m

B)

h'/h = s1'/s1

h' = (1.05/20)*20

h' = 1.05 cm

c)

real

d)

inverted

reduced

perverted

2)

na/s + nb/s' = (nb-na)/R

1.5/20 + 1/s' = (1-1.5)/5

s' = -5.714 cm

A) s' = -5.714 cm

B)

h'/h = s'/s

h' = (5.714/20)*2 = 0.5714 cm

C)

inside

virtual

erect

reduced

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