Phys 131 HW#2
Q#1 Red laser beam enters hits glass/ water interface with an angle of 30° find the
angle of the refracted beam in the water. (20)

Angle of refraction:

Explanation:

Refraction is a phenomenon that occurs when light crosses the interface between two mediums.

When this occurs, the ray of light bends, according to Snell's law:

where

are the index of refraction of the two mediums, respectively

is the angle of incidence (the angle between the incident ray and the normal to the surface)

is the angle of refraction (the angle between the refracted ray and the normal to the surface)

In this problem, we have:

(index of refraction of glass for red light)

(index of refraction of water for red light)

(angle of incidence)

Therefore, the angle of refraction is:

Explanation:

cross sectional area A = 40 cm² = 40 x 10⁻⁴ m² , n = 40 , Magnetic field B = 2 T . Current = I .

Maximum torque = 2 x 10⁻⁶ Nm

Value of maximum torque = n B A I .

n B A I = 2 x 10⁻⁶ Nm

40 x 2 x 40 x 10⁻⁴  I =  2 x 10⁻⁶ Nm

.32 I  = 2 x 10⁻⁶ Nm

I = 2  x 10⁻⁶ / 32 x 10⁻²

= .0625 x 10⁻⁴

= 6.25 x 10⁻⁶

= 6.25 μ A .

b )

Work done in rotating a coil = n B A I ( cos θ₂ - cosθ₁ )

= n B A I ( cos θ₂ - cosθ₁ )

= 2 x 10⁻⁶ ( cos 180 - cos θ )

= 2 x 10⁻⁶ ( -1  - cos θ )

= - 2 x 10⁻⁶ ( 1  + cos θ ) J .