Optics Answers

the refrective indeces for core and cladding for step index fiber is 1.52 & 1.41 respectively. calculate critical angle,numerical aperature,maximum incident angle

why a re-chargable batteries charging more faster than discharging? what mechanism occur while charging and discharging?

I keep reading about how the sky isn’t actually blue, but violet.
Such as here: http://answers.yahoo.com/question/index?qid=20090324145007AAdcahf


(Please answer all of these if you can help me)

1.) Are these statements about the sky really being violet true or just rumors?

2.) If it is true, is there a way of knowing the sky’s exact shade of violet?

3.) I have to figure this out. What is the real obstacle for us not being able to see it?
From what I've read, it's one of these two:

- Ozone

- Ultraviolet radiation

- Or is it both?

a wave pulse is traveling on a string of linear mass density 1.0g/cm under a tension of 1 kg weight .calculate the time taken by the pulse to travel a distance of 50cm on the string .(g=9.8 meter per second square)

Does the law of specular reflection (angle in = angle out) of an obliquely incident light ray still hold if the mirror surface is moving in a direction parallel to the surface normal. Does it matter if the motion is towards or away from the stationary light source with uniform or changing velocity?