MCQ
The graph shows how the magnification $45^{\circ}$ produced by a convex thin lens varies with image distance $v$. What was the focal length of the used
- A$\frac{b}{c}$
- B$\frac{b}{c a}$
- C$\frac{b c}{a}$
- ✓$\frac{c}{b}$
✓
Answer
Correct option: D.
$\frac{c}{b}$
For a lens $m=\frac{f-v}{f}=-\frac{1}{f} v+1$ Comparing it with $y=m x+c$Slope $=m=-\frac{1}{f}$
From graph, slope of the line $=\frac{b}{c}$
Hence $-\frac{1}{f}=\frac{b}{c} \Rightarrow|f|=\frac{c}{b}$
From graph, slope of the line $=\frac{b}{c}$
Hence $-\frac{1}{f}=\frac{b}{c} \Rightarrow|f|=\frac{c}{b}$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
It takes 10 minutes to cool a liquid from $61 C$ to $59 C$. If room temperature is $30 . C$ then time taken in cooling from $5 \mathrm{l} C$ to $49 C$ is
→In adiabatic expansion of a gas
A body starts from rest. What is the ratio of the distance travelled by the body during the 4 th and 3 rd second
Two thin lenses whose powers are $+2 D$ and $-4 D$ respectively combine, then the power of combination is
→If the refractive indices of a prism for red, yellow and violet colours be $1.61,1.63$ and $1.65$ respectively, then the dispersive power of the prism will be
→No other thermometer is as suitable as a platinum resistance thermometer to measure temperature in the entire range of
In a compound microscope the objective of $f_o$ and eyepiece of $f_e$ are placed at distance $L$ such that $L$ equals
→The pressure of air in a soap bubble of $0.7 \mathrm{~cm}$ diameter is $8 \mathrm{~mm}$ of water above the pressure outside. The surface tension of the soap solution is
→Henry/ohm can be expressed in
A vertical U-tube of uniform inner cross section contains mercury in both sides of its arms. A glycerin (density $=1.3 \ g / cm$ ) column of length $10 \ cm$ is introduced into one of its arms. Oil of density $0.8\ gm / cm$ is poured into the other arm until the upper surfaces of the oil and glycerin are in the same horizontal level. Find the length of the oil column, Density of mercury $=13.6\ g / cm$
→