An insect 550 mm tall is placed 200 cm to the left of a thin
An insect 5.50 mm tall is placed 20.0 cm to the left of a thin planoconvex lens. The left surface of this lens is flat, the right surface has a radius of curvature of magnitude 12.2 cm , and the index of refraction of the lens material is 1.70.
Part A
Calculate the location of the image this lens forms of the insect.
230.4
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Part B
Calculate the size of the image.
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Part C
Is the image real or virtual? erect or inverted?
The image is Please Choosereal and erect real and inverted virtual and erect virtual and inverted .
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| s = | 230.4 | cm |
Solution
A.
1/f = (n - 1)(1/R1 - 1/R2)
When R1 tends to infinity, then R2 = -12.2 cm
1/f = (1.70 - 1)*(1/infinity - 1/(-12.2))
1/f = [0.70*(0 + 1/12.2)]
f = [0.70*(0 + 1/12.2)]^-1 = 17.42 cm
Now
1/u + 1/v = 1/f
u = 20 cm
f = 17.42 cm
v = uf/(u - f)
v = 17.42*20/(20 - 17.42)
v = 135.03 cm
B. m = -v/u = -135.03/20 = -6.75
m = hi/ho
hi = m*ho = -6.75*5.5 mm = -37.125 mm
C. v is positive means image is real
hi is negative means image is inverted
Let me know if you have any doubt.

