Question

#2

a)Place a nickel under the center bottom of an empty beaker. Look at the nickel from the side of the beaker. Pour water in the beaker. Can you see the nickel from the side? Repeat with the nickel inside the beaker. Use ray diagrams and your knowledge of refraction to explain the two situations observed.

b)Find the magnification for the object below which is 40 cm from the thin lens which is formed by cutting two spherical shapes from glass with index of refraction 1.8 and radii of 20 cm and 18 cm.

Answer 1

(b) Using a len's maker formula, we have

1 / f = (n - 1) [(1 / R₁) - (1 / R₂)]

where, n = refractive index of glass = 1.8

R₁ = radius of first sphere = 20 cm

R₂ = radius of second sphere = 18 cm

then, we get

1 / f = (1.8 - 1) [1 / (20 cm) - 1 / (18 cm)]

1 / f = (0.8) [(-1 / 180) cm]

1 / f = - (0.00444 cm)

f = - 225.2 cm

Using a len's formula, we have

1 / d₀ + 1 / d_i = 1 / f

1 / d_i = 1 / (-225.2 cm) - 1 / (40 cm)

1 / d_i = - (0.0294405 cm)

d_i = - 33.9 cm

We know that, m = - d_i / d₀ - [(-33.9 cm) / (40 cm)]

m = 0.847