Question

# Lenses of powers $$3D$$ and $$-5D$$ are combined to from a composite lens. An object is placed at a distance of $$50\ cm$$ from this lens. Calculate the position of its image.

A
10 cm
B
+10 cm
C
25 cm
D
+25 cm

Solution

## The correct option is C $$-25\ cm$$Given, Power $${{P}_{1}}=+3D\ \ and\ {{P}_{2}}=-5D$$ Position of object $$u=-50\,cm$$ Power gets added  $$P={{P}_{1}}+{{P}_{2}}$$ $$P=3-5=-2$$ $$f=\dfrac{1}{P}=\dfrac{1}{-2}=-50\,cm$$ Apply lens formula $$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$$ $$v=\dfrac{uf}{f+u}=\dfrac{\left( -50 \right)\times \left( -50 \right)}{\left( -50 \right)+\left( -50 \right)}=-25\,cm$$ Position of image is $$v=-25\,cm\$$ Physics

Suggest Corrections

0

Similar questions
View More

People also searched for
View More