Answer:
[tex]f= +113\ cm[/tex]
Explanation:
Using Lens Maker's formula
[tex]\frac{1}{f}=(n-1)\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right)[/tex]
[tex]R_{1}=+25 cm,\ R_{2}=+45 cm, n=1.5[/tex]
[tex]\frac{1}{f}=(1.5-1)\left(\frac{1}{25}-\frac{1}{45}\right)[/tex]
[tex]\frac{1}{f}=0.5 \times \frac{45-25}{45 \times 25}[/tex]
[tex]\frac{1}{f}=0.5 \times \frac{20}{45 \times 25}[/tex]
[tex]f = 112.5\ cm[/tex]
[tex]f= +113\ cm[/tex]
Hence, focal length is equal to 113 cm.
