Can someone please explain to me how to do these??? 1. At rest, the starship Ent
ID: 2060431 • Letter: C
Question
Can someone please explain to me how to do these???
1. At rest, the starship Enterprise appears light blue, because the paint on its hull reflects light at a visible wavelength of 480 nm. If the ship was moving away from you at 25% the speed of light, what color would appear due to the Doppler shift?
2. You want to make a solenoid that is 38 cm long with 4300 turns. How much current should you run through the solenoid to produce a magnetic field of 0.75 T?
3. Scola likes to play with electrons and flicks them with a speed of 1.3 x 103 m/s thru a hole in a box where a uniform magnetic field of 0.25T exists into the page. Which trajectory, (A or B) will the elctrons follow once they enter the box
Explanation / Answer
1) This is done using the formula for Doppler Shift with relativistic speeds. That formula is...
' = [(1+v/c)/(1-v/c)]
' = (480)([(1 + .25c/c)/(1 - .25c/c)]
' = 619.7 nm
This value is close to red, but still a little orange. Some call is amber red. Depensd on what your book will call it, my guess is they will call is Red.
2) For a solenoid, the formula is
B = oNI/l
(.75) = (4 X 10-7)(4300)(I)/(.38)
I = 52.7 A
3) Path B. By the right hand rule, you place your fingers in the direction of the magnetic field, which in this case, is into the field. Then you place your thumb in the direction of the velocity of the positive charge. Since we have an electron (negative charge) flowing right, you need to point your thumb to the left.
When your thumb is left, and your fingers are into the page, your palm faces downward. That is the direction of the applied force, so path B is the choice.