# Tutor profile: Huseyin O.

## Questions

### Subject: Physics (Waves and Optics)

Find the thickness of a soap film that gives constructive second-order interference of reflected red light (λ=7000Ά). the index of refraction of the film is 1.33. Assume a parallel beam of incident light detected at 30degree to the normal

within a limited region, the film can be considered as a parallel-sided slap of n=1.33. The optical path difference of the beams reflected at the upper and lower surfaces is: Δ=2ndcosΘ +λ/2 for constructive second-order interference, we have Δ =2λ d=3λ/(4ncosΘ) where Θ is the angle of reflection inside the film. From Snell's law, we have SinΘ=SinΘ` = 1/(2n) cosΘ=√1-(1/2n)^2 which yields d=4260Ά

### Subject: Physics (Newtonian Mechanics)

Calculate the moment of inertia of a solid sphere about an axis through its center

Imagine the sphere of mass M and radius R to be made of a series of circular discs, a typical one being of thickness dx at distance x from the center, The area of the disc is π(R^2 – x^2), and if the density of the sphere is ρ, the mass of the disc is ρ π(R^2 – x^2) dx. The elementary moment of inertia of the disc about the axis OX is1/2 (mass)(radius)2 dI =1/2*πρ (R^2 - x2)dx(R^2 - x2) Hence the moment of inertia of the sphere is the summation of dI between 0 and R I= (8πρ/15)R^5 = 2/5 MR^2 As: ρ =3M /4π R^3

### Subject: Physics

Calculate the velocity of the Earth relative to the Sun given that the light traveling from the sun takes 8 minutes and 20 seconds to reach the earth

Firstly we should suppose that the trajectory of the earth is a CIRCLE, then the radius of the circle is the distance between the sun and the earth and we can easily calculate it since the velocity of the light is V=3 X 10^8 m/sec and the light takes 8minutes and 20 seconds to reach the earth then the distance between the earth and the sun is R= V *T(time)=3 X 10^8*500(time in seconds)=15 X 10^10meter. After that, we can easily calculate the circumference of the circle S= 2πR=2π*15*10^10=94.2*10^10 M Now the earth takes one year(approx 365 days) to pass this distance, which means that we Know the time (t=365*24*60*60 sec) that the earth takes to pass this distance and we know the distance we can easily calculate the velocity of the earth relative two the sun v= S/t = 29870.62405 m/s

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