Question

Figure 34-25 shows a fish and a fish stalker in water. (a) Does the stalker see the fish in the general region of point a or point b? (b) Does the fish see the (wild) eyes of the stalker in the general region of point c or point d?

Short answer

(a) The stalker spots the fish in or near point a.

(b) Around point c, the fish can roughly make out the stalker's eyes.

Step-by-step solution

The given data

Fig. 34-25 showing a fish and a fish stalker in water is given.

Understanding the concept of refraction

For a material with a higher refractive index, the light bends towards the normal line; while for a material with a low refractive index, it speeds up and bends away from the normal line. Analyzing the given figure and using the concept of refraction we can find the region in which the stalker sees the fish and the fish sees the eyes of the stalker.

(a) Calculation of the view through the eyes of a stalker

The ray diagram:

Light refracts away from the normal when it moves from a rarer to a denser medium, and towards the normal when it moves from a rarer to a denser media.

The ray of light is travelling from water to air, or from the denser medium to the rarer medium, according to the ray diagram above. As a result, the light should refract differently than usual. Therefore,

This is only conceivable in region a, as shown in the image.

Therefore, the stalker spots the fish in or near point a.

(b) Calculation of the view through the eyes of a fish

The ray diagram:

The beam of light is moving from air to water, or from the rarer medium to the denser medium, according to the ray diagram above. In order to return to normal, the light should do so. Thus,

This is only conceivable in region c, as shown in the image.

Therefore, the around point c, the fish can roughly make out the stalker's eyes.