A convex lens of power 5D and a concave lens of power 7.5D are placed in contact with each other. What is the:
Power of this combination of lenses?
Focal length of this combination of lenses?
Download our app for free and get started
$P_1=+D, P_2=-7.5 D$
a. Power of combination,
$P=P_1+P_2$
$=+5 D+(-7.5 D)=-2.5 D$
b. Focal length of the combination,
$f=\frac{1}{P}=\frac{1}{-2.5}=-0.4 m=-40 cm$
Download our app
and get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close focal contact with each other. Calculate the lens power of this combination.
Describe with the help of a diagram, the nature, size and position of the image formed when an object is placed beyond the centre of curvature of a concave mirror.
The linear magnification produced by a spherical mirror is +3. Analyse this value and state the (i) type of mirror and (ii) position of the object with respect to the pole of the mirror. Draw ray diagram to show the formation of image in this case.
If the image formed by a spherical mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a labelled ray diagram to support your answer.
The refractive index of water with respect to vacuum is $\frac{4}{3}$ and refractive index of vacuum with respect to glass is $\frac{2}{3}$ If the speed the speed of light in glass is $2 \times 10^8 ms^{-1}$, find the speed of light in (i) vacuum, (ii) water.