Jawabanmu

2014-05-19T19:51:36+07:00
1) 

1/f = 1/s + 1/si
1/15= 1/25 + 1/si
1/15 - 1/25 = 1/si
25-15/375 = 1/si
10/375 = 1/si
375= 10si
37,5 = si (bayangan)

rumus perbesaran :

M= Si/So atau Hi/Ho
M= 37,5 / 25 
M = 1,5


3)  n1 sin1 = n2 sin2

n = indeks bias
sin 1 = sinar datang
sin 2 = sinar bias

1,33 . sin45 = 1,5 . sinx
1,33 . 1/2 akar 2 = 1,5 . sinx
2,66 = 1,5 .sin x
2,66 / 1,5 = sin x
1,773 = sin x

maaf kalau cuma bisa segini aja :)