Speed of light in different media

AI Thread Summary
The discussion revolves around calculating the speed of light in various media, specifically air, water, diamond, and perspex, using the refractive index formula. The refractive index is defined as the speed of light in a vacuum divided by the speed of light in the medium. Users are encouraged to look up the specific speeds online, as the information is readily available. The speed of light in a vacuum is approximately 300,000 km/s, which serves as a reference point for these calculations. Utilizing Google for quick answers is emphasized as a helpful resource.
vrus
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Light is not my most favouite topic, but I am forced to do it at school ! :mad:

Anyway, my homework was to find the refracting index of light in water, air, diamond and perspex. But they said we have to show the working out ! :bugeye:

So can anyone please tell me the speed of light in :-
(i) Air
(ii) Water
(iii) Diamond
(iv) Perspex
This is urgent !
I require it in km/s.
Thanks !
 
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First look for refractive indexes of all the mediums you referred above.

then refractive index of a medium= speed of light in vacuum/speed of light in that medium

Speed of light in vacuum = 300000000 m/s
 
vrus,

So can anyone please tell me the speed of light in :-

(i) Air
(ii) Water
(iii) Diamond
(iv) Perspex

Here are the answers:

(i) google: speed of light in air
(ii) google: speed of light in water
(iii) google: speed of light in diamond
(iv) google: speed of light in Perspex

Google is your friend! Learn to use it.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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