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The power of a lens is +2.0 D. What is its focal length?
0.5 m
0.2 m
1.0 m
2.0 m
0.5 m
The power of a lens (P) is defined as the reciprocal of its focal length (f) in meters. Given P=+2.0┬аD, the focal length is calculated as f=P1тАЛ=2.01тАЛ=0.5┬аm.
The power of a lens (P) is defined as the reciprocal of its focal length (f) in meters. Given P=+2.0┬аD, the focal length is calculated as f=P1тАЛ=2.01тАЛ=0.5┬аm.
Think of a magnifying glass with a higher power as having a 'tighter' focus, meaning it brings light together over a shorter distance compared to a lower power lens.
P-F-I: Power = Fraction Inverse, i.e., P=f1тАЛ.
P=f(m)1тАЛ тАФ Relationship between power P in Diopters and focal length f in meters
f=P100тАЛ тАФ Formula used if the focal length is required in centimeters (cm)
The power of a lens measures its ability to converge or diverge light rays. A positive power indicates a converging lens (convex), where the focal length is defined as the distance from the optical center to the point where parallel light rays meet. The SI unit for power is Diopter (D), which corresponds to mтИТ1.
The power of a convex lens is always positive (+).
The power of a concave lens is always negative (-).
1 Diopter is defined as the power of a lens with a focal length of 1 meter.
Standardized unit allows for easy calculation of combined lens systems by simple addition.
Does not account for spherical or chromatic aberrations inherent in real-world lenses.
Prescription spectacles for hypermetropia (farsightedness).
Design of compound microscope and telescope objectives.
The unit Diopter (D) is equivalent to mтИТ1.
Option B (0.2 m) would imply P=5┬аD. Option C (1.0 m) would imply P=1┬аD. Option D (2.0 m) would imply P=0.5┬аD.
A is correct тАФ The focal length is the reciprocal of the power, resulting in 0.5┬аm.
Always ensure the focal length is in meters before using the formula P=f1тАЛ. If the value is in cm, convert it to m first to avoid calculation errors.
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