Skip to main content

No. Of imageimages

Multiple Images with Plane Mirrors

Introduction

The number of images formed by two adjacent plane mirrors depends on the angle between the mirror. If θ (in degrees) is angle between the plane mirrors then number of images are given by,

n=n=360θ1.

We verify this formula in this experiment.

Apparatus

Two plane mirrors, protractor to measure angle, candle, matchbox.

Procedure

uba.png

Take two plane mirrors (without frame). Place both the mirrors side by side and fix the junction where they meet with a cello tape. Now you will be able to open and close the mirrors like a book. Place both the mirrors at a small angle apart in the upright position on the floor. Place a lighted candle in the space between the two mirrors. You will observe many images of the candle which makes a beautiful scene.

Now, by gradually decreasing the angle between the mirrors observe the images being formed. You will now observe more and more numbers of images of the candle. Similarly, if the angle between the mirrors is increased the number of images decreases and when this angle is 180 degree, only one image is visible.

When the angle between the two mirrors is 180 degree they together act like a single mirror so that only one image is visible. As the angle between the mirrors gradually decreased, not only the candle but the mirrors themselves get imaged in one another. That is why when the angle between the mirrors is decreased one observe image within image, and image within that image, and so on. In this way one observes a lot many images. If the angle between the mirrors is finally decreased to zero, infinite images are expected to be formed.

  1. Place both the mirrors vertically with 180 degree angle between the them.
  2. Place a lighted candle in the space between the two mirrors.
  3. You will see single image of the candle in mirror. Reduce the angle between mirrors and observe multiple images of the candle which makes a beautiful scene.
  4. Now, measure the maximum angle between two mirrors when you get 1, 3, 5, 7, and 9 images. These angles are θmeasured.
  5. Calculate θcalculated for n=1,3,5,7,9 by using the formula given above.
  6. Draw the ray diagram when angle between two mirrors is 90 degree.

Discussion

nθmeasuredθcalculatedΔθerror
1   
3   
5   
7   
9   

Note

Fill a transparent glass tray with water and fix two similar mirrors at its opposite ends. See the image being formed. What you see is a very long water canal. Think how this happens?

This setup is also used to make a funny game. Make a cap with two strips of different colors (say black and white) pasted on the left and the right side. Adjust the angle between the mirrors so that you see two images of yourselves (with cap and strips clearly visible). Ask your friend to wear the cap and see his image in the mirrors. Order him to touch the white or black strip quickly. There is a great chance that your friend gets confused and end up touching wrong color strip. Why this happened?

Comments

Popular posts from this blog

CBSE syllabus for class 1 to 12

CBSE Syllabus contains the list of topics and subtopics to be covered in the course of study during an academic year. Syllabus for CBSE includes a summary and list of chapters to be studied during the teaching and learning process in a particular class. Most of the national entrance exam ask questions based on CBSE syllabus. Every year  CBSE  issues the syllabus for class 1 to 12. Right from the basic information to a detailed one, the syllabus contains all the information needed by a student and the teacher. Here we have provided the CBSE curriculum for class 1 to class 12 in a detailed manner for all the subjects. NCERT releases the books which are purely based on the CBSE syllabus. Students are strictly recommended to study from  NCERT Books . To every student, it’s important to know the syllabus at the beginning of the academic session. This will help them in understanding what they have to study in the entire year. Also, they can plan their studies in advance. C...

Class 8 Chapter 11 Time and Work

 Access answers to Maths RD Sharma Solutions For Class 8 Chapter 11 Time and Work 1. Rakesh can do a piece of work in 20 days. How much work can he do in 4 days? Solution: The given details are, Time taken by Rakesh to do a piece of work is 20 days Work done by Rakesh in 1 day = 1/20 Work done by Rakesh in 4 days = 4 × 1/20 = 1/5 ∴ 1/5th work can be done by Rakesh in 4days. 2. Rohan can paint 1/3 of a painting in 6 days. How many days will he take to complete painting? Solution: The given details are, Number of days taken by Rohan for painting 1/3 of painting is 6 days Number of days taken by Rohan to complete the painting = 6/(1/3) = 6 × 3 = 18 ∴ Rohan can complete painting in 18days. 3. Anil can do a piece of work in 5 days and Ankur in 4 days. How long will they take do the same work, if they work together? Solution: The given details are, Anil can do a piece of work in 5 days Work done by Anil in 1 day = 1/5 Ankur can do same work in 4 days Work done by Ankur in 1 day = 1/4 Wor...

Tricky and hard math problems

 Here are some fun, tricky and hard to solve maths problems that will challenge your thinking ability.  1. If 1=3 2=3 3=5 4=4 5=4 Then, 6=? Answer: is 3, because ‘six’ has three letters 3 2. What is the number of the parking space covered by the car?   This tricky math problem went viral a few years back after it appeared on an entrance exam in Hong Kong… for six-year-olds. Supposedly the students had just 20 seconds to solve the problem! Answer: 87 Believe it or not, this “math” question actually requires no math whatsoever. If you flip the image upside down, you’ll see that what you’re dealing with is a simple number sequence. 3. Replace the question mark in the above problem with the appropriate number.   Answer: 6 4. Which number is equivalent to 3^(4)÷3^(2) This problem comes straight from a standardized test given in New York in 2014. Answer: 9 5. There are 49 dogs signed up for a dog show. There are 36 more small dogs than the large dogs. How many sm...