# Wave and optics help

#### GingerFish

hey guys i have two questions that i wouldn't mind some help on !

firstly
a wave in the form (in meters) of y = 0.5sin(4(pi)t+0.5(pi)x) where t and x are time and space co-ordinates in seconds and meters

find the wave length amplitude frequency and speed of the wave.
is the wave traveling in the +x or -x direction?

and

a hand glider is flying at an altitude of h=125m, green light of wavelength 555nm enters the pilots eye through a pupil that has a diameter D = 2.5mm. the average index of refraction of the material in the eye is n = 1.36.
Determine how far aprt two point objects must be on the ground if the pilot is to have any hope of distinguishing them.

any help will be great!

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#### Galileo

Homework Helper
Hi Gingerfish.

I guess you could just look into your book and see how you can get the speed of the wave, the wavelength and so on.

I usually don't remember all these relations, but you can recover them easily from the formula.
To know the wavelength, imagine taking a snapshot of the wave at a certain instant and then measure the length of one complete period. That is the wavelength. So just put t=0, x=0 ($\sin(0)$)and see how far to the right you have to go to finish one complete revolution (at $\sin(2\pi)$).
You can do a similar thing for the period of revolution (which is easily related to the frequency).
I`m sure you can find the amplitude. If not, read your book.

#### GingerFish

thanks

thanks man i'm working at it, but i don't have any of the course notes at the moment and they havn't been uploaded to the university web space yet

so i don't have any of the formula's handy and i don't know them off by heart

i wouldn't post if i could just look it up, i couldn'd fins anything helpful with google

i'm not lazy!

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