In a pond of water, a flame is held 2 m above the surface of water. A fish is at depth of 4 m from water surface. Refractive index of water is . The apparent height of the flame from the eyes of fish is:
- (A) m
- (B) m
- (C) m
- (D) m
Correct Answer
The Correct Option is D
Approach Solution - 1
Given:Depth of the fish from the surface of the water = 4 mHeight of the flame BC = 2 mRefractive index of the water, We have to find the the apparent height of the flame from the eyes of the fish. The ray diagram is shown below:
Approach Solution -2
Real Depth and Apparent Depth
Real Depth is the real distance of an object under the surface as determined by immersing it with an accurate ruler.
The depth of an item in a denser media, as perceived from a rarer medium, is referred to as apparent depth in a medium. Its value is less than the real depth.
The relationship between the real depth and the apparent depth is given by
Real depthApparent depth=21=21
Where
- 𝜇2 = refractive index of the denser medium
- 𝜇2 = refractive index of the rarer medium
- 𝜇12 = refractive index of the denser medium with respect to the rarer medium
If an object lying in denser medium and is observed from rarer medium, then
Real depthApparent depth=21>1
⇒ Real depth > Apparent depth
That is why, the river bed appeared shallow
If an object lying in rarer medium and is observed from denser medium, then
Real depthApparent depth=21<1
⇒ Real depth < Apparent depth
That is why high flying airplanes appear to be higher than its actual height.
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