[tex]{ \qquad\qquad\huge\underline{{\sf Answer}}} [/tex]
Here's the solution ~
According to snells law :
[tex]\qquad \sf \dashrightarrow \: n_1 ×sin \: i = n_2 \times sin \:r [/tex]
- i = angle of incidence
- r = angle of refraction
[ n corresponds to the refracting index of a medium ]
now, as we know :
- retractive index of air is approximately 1
- angle of incidence is given to be 40°
- refrctive endex of water is given 1.33
Now, let's proceed according to the formula ~
[tex]\qquad \sf \dashrightarrow \: 1 \times \sin(40 \degree) = 1.33 \times \sin(r) [/tex]
[tex]\qquad \sf \dashrightarrow \: \sin(r) = \cfrac{1 \times sin \: r}{1.33} [/tex]
[ sin 40° = 0.6428 ]
[tex]\qquad \sf \dashrightarrow \: \sin(r) = \cfrac{0.6428}{1.33} [/tex]
[tex]\qquad \sf \dashrightarrow \: \sin(r) \approx \cfrac{1}{2} [/tex]
[tex]\qquad \sf \dashrightarrow \: r \approx 30 \degree[/tex]
Hence, the angle of refraction is equal to 30°
