Question

An optic fiber is made of clear plastic with index of refraction of 1.72. For what angle of incidence will light remain within the plastic guide"? A conducting rod whose length is 15 cm is placed on U-shaped metal wire that has a resistance R of 7 ohm as shown in figure 23-9. the wire and the rod are in the plane of the paper. A constant magnetic fields of strength 0.2 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 5 m/s. What is the magnitude of the induced emf in the wire? A step-down transformer is needed to reduce a primary voltage of 120. V AC to 12.0 V AC. What turns ratio is required? A proton is first accelerated from rest through a potential difference V and then enters a uniform 0.60-T magnetic field oriented perpendicular to its path. in this field, the proton follows a circular are having a radius of curvature of 2.84 cm. What was the potential difference V? A 10.0-mu F capacitor is connected to an ac signal with a frequency of 60 Hz. If the maximum voltage applied to the capacitor is 12.0 V, what is the capacitive reactance? A 110-V rms voltage at 50.0 hz is applied across an inductor, a capacitor, and a resistor in series. If the rms value of the current in this circuit is 0.600 A, what is the impedance of this circuit?

Answer 1

for light to ramin inside the fiber light must go through total internal reflection

so

by snell's law

sin (critical angle) / sin r = refractive index of air / refractive index of fibre

in case of critical angle, angle of refraction will be 90 degree

sin (critical angle) / sin 90 = 1 / 1.72

critical angle = 35.55 degree

so,

for angle of incidence greater than 35.55 degree the light will go through total internal reflection