Sign Convention in Ray Optics

Q.

The focal length f of a mirror is given by $\frac{1}{f}=\frac{1}{u}+\frac{1}{v}$ where u and v represent object and image distances respectively. The fractional error in 'f' is given by

1. 

2. 

3. 

4. 

Q. The focal length of a concave mirror has a negative value.

1. False
2. True

Q. How to find angular displacement

Q.
According to sign convention, which of the distances measured in the figure are considered to be negative?

1. a, b
2. c, b
3. a, d
4. c, d