Chapter 34, Problem 1Q

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?

Figure 34-25 Question 1.

To determine

To find:

a) Whether the stalker sees the fish in the general region of point a or point b.

b) Whether the fish sees the eyes of the stalker in the general region of point c or point d.

Answer to Problem 1Q

Solution:

a) The stalker sees the fish in the general region of point a.

b) The fish sees the eyes of the stalker in the general region of point c.

Explanation of Solution

1) Concept:

Analyzing the given figure and using concept of refraction we can find the region in which the stalker sees the fish and the fish sees the eyes of the stalker.

2) Given:

Fig. 34-25.

3) Calculations:

a) The ray diagram:

When light travels from rarer to denser medium, it refracts towards the normal and when it travels from denser to rarer medium, it refracts away from the normal.

From the above ray diagram, we can conclude that, the ray of light is travelling from water to air, that is, from the denser medium to the rarer medium. Hence, the light should refract away from the normal. That is,

${\theta }_r>{\theta }_i$

From the figure, we can conclude that this is possible only in region a.

Therefore, the stalker sees the fish in the general region of point a.

b) The ray diagram:

From the above ray diagram, we can conclude that the ray of light is travelling from air to water, that is, from the rarer medium to the denser medium. Hence, the light should refract towards the normal. That is,

${\theta }_i>{\theta }_r$

From the figure, we can conclude that, this is possible only in region c.

Therefore, the fish see the eyes of the stalker in the general region of point c.

Conclusion:

When the light travels from rarer to denser medium, it refracts towards the normal and when it travels from denser to rarer medium, it refracts away from the normal.