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I need the answer in details ... and please understand that I struggle a little in English .. physics
Sep 1, 2014

#1
+8

The lens formula is:

$${\frac{{\mathtt{1}}}{{\mathtt{f}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{1}}}{{\mathtt{d1}}}} = {\frac{{\mathtt{1}}}{{\mathtt{d2}}}}$$

In which

f: focal length

d1:distance to source

d2:distance to image

Since the sun has an almost infinite distance to the lens d1=infinity, which means:

$${\frac{{\mathtt{1}}}{{\mathtt{\infty}}}} = {\mathtt{0}}$$

so

$${\frac{{\mathtt{1}}}{{\mathtt{f}}}} = {\frac{{\mathtt{1}}}{{\mathtt{d2}}}}$$

Which means answer A is correct.

Sep 1, 2014

#1
+8

The lens formula is:

$${\frac{{\mathtt{1}}}{{\mathtt{f}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{1}}}{{\mathtt{d1}}}} = {\frac{{\mathtt{1}}}{{\mathtt{d2}}}}$$

In which

f: focal length

d1:distance to source

d2:distance to image

Since the sun has an almost infinite distance to the lens d1=infinity, which means:

$${\frac{{\mathtt{1}}}{{\mathtt{\infty}}}} = {\mathtt{0}}$$

so

$${\frac{{\mathtt{1}}}{{\mathtt{f}}}} = {\frac{{\mathtt{1}}}{{\mathtt{d2}}}}$$

Which means answer A is correct.

Honga Sep 1, 2014