Lens Power Calculation
The power of a lens is defined as the reciprocal of its focal length when the focal length is measured in meters.
Formula and Calculation
The formula relating power ($P$) and focal length ($f$) is:
$ P = \frac{1}{f} $
Where:
- $P$ is the power of the lens in Diopters (D).
- $f$ is the focal length in meters (m).
Step-by-Step Solution
- Convert Focal Length: The given focal length is $f = 25\text{ cm}$. Convert this to meters:
$ f = 25\text{ cm} = \frac{25}{100}\text{ m} = 0.25\text{ m} $
- Calculate Power: Use the formula $P = \frac{1}{f}$ with the focal length in meters.
$ P = \frac{1}{0.25\text{ m}} $
$ P = 4\text{ D} $
Therefore, the power of the lens is $4\text{ D}$.
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Important Questions from Optics
Which one of the following colours may be obtained by combining green and red colours?
Which of the following are the primary colours of light?
Directions: The following items consist of two statements, Statement I and Statement II. You are to examine these two statements carefully and select the answers to these items using the code given below:
Statement I: Diamond is very bright.
Statement II: Diamond has very low refractive index
A non-SI unit called 'nit' is the unit of which of the following photometric quantities used to measure a multitude of light intensity?
Which among the following is used as a reflector in search lights?
