# Civil Engineering - Surveying - Discussion

Discussion Forum : Surveying - Section 2 (Q.No. 7)
7.
The angle between two plane mirrors of optical square, is
20°
30°
45°
60°
90°.
Explanation:
No answer description is available. Let's discuss.
Discussion:
7 comments Page 1 of 1.

Lalit said:   4 years ago
In surveying optical square is used to setting out right angles. The horizon glass is placed at an angle of 120° with the horizon sight and index glass is placed at an angle of 105° with the index sight.

Anomi said:   5 years ago
In the SINGLE optical square, it contains two reflective planes inside, and the angle between two planes is 45°.

Sameer sopori said:   6 years ago
@All.

In the SINGLE optical square, it contains two reflective planes inside, and the angle between two planes is 45°,

Just draw these 4 angles of optical square on a paper, you will understand it easily 45°, 90°, 112.5 °, 112.5°, (the two planes are at 45° inside the optical square).

Thanks.
(1)

Eddie Murphy said:   6 years ago
It should be equal to 45°only. It having two squares.

Balaji shesherao jadhav said:   6 years ago
It should be equal to 45° only. It has two squares.

MADDEESWAR REDDY said:   6 years ago
It should be equal to 45° only. It has two squares.

Sameer kashmiri said:   1 decade ago
When we keep two mirror at an angle 45°, it will make angle of 90° by double mirror reflection.