Solve the Reflection of Lake-Bed: A 10m Deep Diving Challenge

[lecker1003]

hi, i got a real problem. i have a question here and have absolut no clue what i have to do and which equation i have to use...

( for my shame, i was sick at that time we done it in school..)

question:

A diver is at the bottom of a lake, which is 10m deep. if he looks straight up he sees the sky, but if he looks at the surface of the water a little further away he sees a reflection of the lake-bed in the calm surface. calculate the distance from his position to the nearest point on the bed that he can see clearly in the reflection. take the refraktive index of the water as 1.33, and of the air as 1.

i really was thinking about it, but i have no clue what i have to do...

 

[berkeman]

What can you tell us about "total internal reflection"? Your textbook will have introduced this concept before asking you that question. Or you can just google that expression, or check wikipedia.org. Now can you show us how you calculate that angle in the problem?

 

[lecker1003]

i don't got a textbook.. we getting notes only.. and i don't have them.. i tried too google biut i don't find anything

 

[berkeman]

Go to www.wikipedia.org, and do the search on Total Internal Reflection. Tell us what you find out about the "critical angle". Now you're good to go! Be sure to show your work.

 

[lecker1003]

other prob

so, i have another prob too:

i tried to calculate b:

a. Draw a diagram to show a convex lens of focal length 10cm being used as a simple microscope( magnifying glass) producing an image at the distance of distinct vision -- erledigt!

b. what is the angular magnification of this arrangement?

c. what would be the angular magnification be if the image were infinity?


i got m= d/f = 25/10 = 2.5

can that be right?

 

[lecker1003]

also i just looked in wikipedia with:

Total Internal Reflection and critical angle.. but it don't help me at all..

i don't understand the prinzip

 

[daniel_i_l]

Do you know snells law? inoreder do see the bottom of the lake does the light coming from the bottom to the surface have to be reflected or refracted? at what angle can it do what it has to?
HINT: http://en.wikipedia.org/wiki/Total_Internal_Reflection#Critical_angle

 

[lecker1003]

ok

also i understand the basic now.. the picture. but i don't know really what i have to calculate..

i know 10m to the surface when he looks straight up. what is 90 degree with the bottem

the next i know is the tir should be 48.6 degree.. that's the maxc or its not anymore refracting..

but know i stock and i discussed it with a friend and nearly he shoot me...

3hrs long and still no clue...

pls

and i have 4 more questions i don't know lol

 

[lecker1003]

ok i got it now.. but now i got next problem


float(2*10*tan(arcsin(1/1.33))) = 22.80841284


this one:


a compound microscope is made using a 2cm focal length lens as objectiv an a 10cm focal lenth lens an a eyepiece. the lenses are sepeerated by 30cm, and the final image is viewed at the distance of dinstinct vision


question: calculate distance between object and first lense