Math Problem Statement

A student places an object of height 10.0cm near a converging lens, and it creates a real image at a distance of 60.0cm away from the lens. The lens has a focal length of magnitude 20cm. Calculate object distance, magnification, image height, size, and orientation of the image.

Solution

To solve this lens problem, we use the following information and equations for a converging lens:

Given:

  • Object height (hoh_o) = 10.0cm10.0 \, \text{cm}
  • Image distance (did_i) = 60.0cm60.0 \, \text{cm} (real image means di>0d_i > 0)
  • Focal length (ff) = 20.0cm20.0 \, \text{cm} (converging lens means f>0f > 0)

We are tasked to determine:

  1. Object distance (dod_o)
  2. Magnification (MM)
  3. Image height (hih_i)
  4. The size and orientation of the image.

Step 1: Use the Lens Formula to find dod_o

The lens formula is:

1f=1do+1di\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}

Rearranging for dod_o:

1do=1f1di\frac{1}{d_o} = \frac{1}{f} - \frac{1}{d_i}

Substitute f=20.0cmf = 20.0 \, \text{cm} and di=60.0cmd_i = 60.0 \, \text{cm}:

1do=120160\frac{1}{d_o} = \frac{1}{20} - \frac{1}{60}

1do=360160=260\frac{1}{d_o} = \frac{3}{60} - \frac{1}{60} = \frac{2}{60}

do=602=30.0cmd_o = \frac{60}{2} = 30.0 \, \text{cm}

So, do=30.0cmd_o = 30.0 \, \text{cm}.


Step 2: Calculate the Magnification (MM)

The magnification is given by:

M=didoM = -\frac{d_i}{d_o}

Substitute di=60.0cmd_i = 60.0 \, \text{cm} and do=30.0cmd_o = 30.0 \, \text{cm}:

M=6030=2M = -\frac{60}{30} = -2

Thus, M=2M = -2.


Step 3: Find the Image Height (hih_i)

The image height is given by:

hi=Mhoh_i = M \cdot h_o

Substitute M=2M = -2 and ho=10.0cmh_o = 10.0 \, \text{cm}:

hi=210=20.0cmh_i = -2 \cdot 10 = -20.0 \, \text{cm}

So, the image height hi=20.0cmh_i = -20.0 \, \text{cm}. The negative sign indicates the image is inverted.


Step 4: Size and Orientation of the Image

  • Size of the Image: 20.0cm20.0 \, \text{cm} (magnitude of hih_i).
  • Orientation of the Image: Inverted (due to the negative sign of hih_i).

Final Answers:

  • f=20.0cmf = 20.0 \, \text{cm}

  • do=30.0cmd_o = 30.0 \, \text{cm}

  • di=60.0cmd_i = 60.0 \, \text{cm}

  • M=2M = -2

  • ho=10.0cmh_o = 10.0 \, \text{cm}

  • hi=20.0cmh_i = -20.0 \, \text{cm}

  • Size of the image: 20.0cm20.0 \, \text{cm}

  • Orientation of the image: Inverted


Do you need further clarification on any step? Let me know!

Related Questions:

  1. How would the results change if the object was placed at twice the focal length?
  2. What happens if the focal length of the lens is reduced?
  3. What kind of image is formed when the object is inside the focal length?
  4. How can you differentiate between real and virtual images using sign conventions?
  5. Can you explain the relationship between magnification and object/image distances?

Tip:

When solving lens problems, always ensure to use proper sign conventions: real distances are positive, and inverted images have negative heights.

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Math Problem Analysis

Mathematical Concepts

Optics
Lens Formula
Magnification

Formulas

Lens Formula: 1/f = 1/d_o + 1/d_i
Magnification Formula: M = -d_i / d_o
Image Height Formula: h_i = M * h_o

Theorems

Lens Formula

Suitable Grade Level

Grades 9-11