An object is placed at a distance of 24 cm from the optic centre of a ...
Hey, use;
u= -24cm
f= -18cm
then,
1/f =1/u+1/v
then you use,
ho/hi=v/u.
An object is placed at a distance of 24 cm from the optic centre of a ...
Given:
- Distance of object from the lens (u) = 24 cm
- Focal length of the lens (f) = 18 cm
To find:
- Distance of the image from the lens (v)
- Height of the image if the object is 30 cm tall
Solution:
Step 1: Identify the type of lens
The given lens is a convex lens since the focal length (f) is positive.
Step 2: Apply the lens formula
The lens formula is given by:
1/f = 1/v - 1/u
Where:
- f is the focal length of the lens
- v is the distance of the image from the lens
- u is the distance of the object from the lens
Substituting the given values into the lens formula:
1/18 = 1/v - 1/24
Step 3: Solve the equation
To solve the equation, we can take the LCM (Least Common Multiple) of 18 and 24, which is 72. Multiplying through by 72, we get:
72/18 = 72/v - 72/24
4 = 72/v - 3
Add 3 to both sides of the equation:
7 = 72/v
Cross-multiply:
7v = 72
Divide both sides by 7:
v = 72/7
Therefore, the distance of the image from the lens is approximately 10.29 cm.
Step 4: Calculate the height of the image
The magnification formula is given by:
magnification (m) = height of image (h') / height of object (h)
The magnification is equal to the ratio of the image height to the object height. Rearranging the formula, we have:
h' = m * h
Where:
- h' is the height of the image
- h is the height of the object
Given that the object height (h) is 30 cm, we need to calculate the magnification.
Using the magnification formula:
m = -v/u
Substituting the values:
m = -10.29/24
m ≈ -0.4292
Since the magnification is negative, the image is inverted.
Now, substituting the values into the height of the image formula:
h' = -0.4292 * 30
h' ≈ -12.88 cm
Therefore, the height of the image is approximately 12.88 cm.
Conclusion:
- The distance of the image from the lens is approximately 10.29 cm.
- The height of the image is approximately 12.88 cm.
To make sure you are not studying endlessly, EduRev has designed Class 10 study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Class 10.