An object of height \(3.0 \mathrm{cm}\) is placed \(5.0 \mathrm{cm}\) in front of a converging lens of focal length \(20 \mathrm{cm}\) and observed from the other side. Where and how large is the image?

Short Answer

Expert verified
The image is formed at a distance of \(4.0\,\text{cm}\) from the lens and has a height of \(2.4\,\text{cm}\).

Step by step solution

01

Write down the given information

Object height, \(h_o = 3.0\,\text{cm}\) Object distance, \(d_o = 5.0\,\text{cm}\) Focal length of the converging lens, \(f = 20\,\text{cm}\)
02

Apply the lens formula

The lens formula relates the object distance (do), image distance (di), and focal length (f). It is given by: \(\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}\) Substitute the given values and solve for di: \(\frac{1}{20\,\text{cm}} = \frac{1}{5.0\,\text{cm}} + \frac{1}{d_i}\)
03

Solve for image distance

To find the image distance, we need to solve the equation for \(d_i\): \(\frac{1}{d_i} = \frac{1}{20\,\text{cm}} - \frac{1}{5.0\,\text{cm}} =\frac{1}{4.0\,\text{cm}}\) Now, take the reciprocal to find \(d_i\): \(d_i = 4.0\,\text{cm}\) So, the image distance is \(4.0\,\text{cm}\).
04

Calculate the magnification

The magnification (M) of a lens is the ratio of image height (\(h_i\)) to the object height (\(h_o\)), and it's also equal to the ratio of image distance (\(d_i\)) to object distance (\(d_o\)): \(M = \frac{h_i}{h_o} = \frac{d_i}{d_o}\) Now, substitute the values and solve for \(h_i\): \(M = \frac{4.0\,\text{cm}}{5.0\,\text{cm}} = \frac{4}{5}\) \(h_i = M \times h_o = \frac{4}{5} \times 3.0\,\text{cm} = 2.4\,\text{cm}\)
05

State the final answer

The image is formed at a distance of \(4.0\,\text{cm}\) from the lens and it has a height of \(2.4\,\text{cm}\).

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