Answer:
A) true. We see the equations and it would appear that the sign changes when you pass from one medium to the other
Explanation:
The expression for the focal length of a thin lens is
1 / f = (n’-n) (/ 1/R₁ - 1 / R₂)
In this equation n ’and n are the refractive indexes of the lens and the surrounding environment respectively
For converging lenses f is positive and for diverging lenses f is negative
Let's write this equation for both media
Air ( n= 1)
1 / f₁ = (1.20-1) (1/R₁ -1/R₂)
1 / f₁ = 0.2 (1/R₁ - 1/R₂)
Water ( n= 1.33)
1 / f₂ = (1.20 -1.33) (1/R₁ -1/R₂)
1 / f₂ = -0.13 (1/R₁ -1/R₂)
We see that the sign of the focal length changes
Now we can analyze the claims
A) true. We see the equations and it would appear that the sign changes when you pass from one medium to the other
B) false. The focal length sign changes
C) False. The two signs change
D) False. The focal length sign changes
E) False. We cannot know the value, but change of characteristic
