The image of a candle flame placed at a distance of 45cm from a spherical lens is formed on a screen placed at a distance of 90cm from the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 2cm, find the height of its image.
Download our app for free and get started
$\text{TSA}=4650$$2(\text{lb}+\text{bh}+\text{lh})=4650$
$\text{u}=-45\text{cm}$
$\text{v}=90\text{cm}$
$\therefore\text{ Lence is convex}$
$\frac{1}{\text{f}}=\frac{1}{\text{v}}+\frac{1}{\text{u}}$
$\frac{1}{\text{f}}=\frac{1}{90}+\frac{1}{45}$
$\frac{1}{\text{f}}=\frac{1+2}{90}=\frac{3}{90}$
$\frac{1}{\text{f}}=\frac{1}{30}=+30\text{cm}$
$\frac{\text{v}}{\text{u}}=\frac{\text{h}_\text{i}}{\text{h}_0}$
$\frac{90}{-45}=\frac{2}{\text{h}_0}\frac{\text{h}_\text{i}}{\text{h}_0}=2$
$\frac{90}{-45}=\frac{\text{h}_\text{i}}{2}$
$\text{h}_\text{i}=\frac{90\times2}{-45}=-4\text{cm}$
$\text{u}=-45\text{cm}$
$\text{v}=90\text{cm}$
$\therefore\text{ Lence is convex}$
$\frac{1}{\text{f}}=\frac{1}{\text{v}}+\frac{1}{\text{u}}$
$\frac{1}{\text{f}}=\frac{1}{90}+\frac{1}{45}$
$\frac{1}{\text{f}}=\frac{1+2}{90}=\frac{3}{90}$
$\frac{1}{\text{f}}=\frac{1}{30}=+30\text{cm}$
$\frac{\text{v}}{\text{u}}=\frac{\text{h}_\text{i}}{\text{h}_0}$
$\frac{90}{-45}=\frac{2}{\text{h}_0}\frac{\text{h}_\text{i}}{\text{h}_0}=2$
$\frac{90}{-45}=\frac{\text{h}_\text{i}}{2}$
$\text{h}_\text{i}=\frac{90\times2}{-45}=-4\text{cm}$
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1View SolutionYou are provided with two lenses of focal length 20cm and 30cm, respectively. Which lens will you use to obtain more convergent light?
- 2QUESTION For the same angle of incidence, the angle of refraction in three different media $A , B$ and C are $10^{\circ}, 25^{\circ}$ and $40^{\circ}$, respectively. In which medium the velocity of light will be maximum?View Solution
- 3View Solution
- An object 3cm high is placed 24cm away from a convex lens of focal length 8cm. Find by calculations, the position, height and nature of the image.
- If the object is moved to a point only 3 cm away from the lens, what is the new position, height and nature of the image?
- Which of the above two cases illustrates the working of a magnifying glass?
- 4View SolutionTo construct a ray diagram we use two rays of light which are so chosen that it is easy to determine their directions after reflection from the mirror. Choose these two rays and state the path of these rays after reflection from a concave mirror. Use these two rays to find the nature and position of the image of an object placed at a distance of 15cm from a concave mirror of focal length 10cm.
- 5View SolutionAn arrow 2.5cm high is placed at a distance of 25cm from a diverging mirror of focal length 20cm. Find the nature, position and size of the image formed.
- 6View SolutionA combination of lenses for a camera contains two converging lenses of focal lengths 20cm and 40cm and a diverging lens of focal length 50cm. Find the power and focal length of the combination.
- 7View SolutionA ray of light enters a diamond from air. If the refractive index of diamond is 2.42, what % (percentage) is speed of light in diamond with that of speed in air?
- 8View SolutionAn object is placed between infinity and the pole of a convex mirror. Draw a ray diagram and also state the position, the relative size and the nature of the image formed.
- 9View SolutionAn object is placed at a distance of 100cm from each of the above lenses A and Calculate:
- Image distance, and
- Magnification, in each of the two cases.
- 10View SolutionA man sits in an optician's chair looking into plane mirror which is 2m away from him and views the image of a chart which faces the mirror and is 50cm behind his head. How far away from his eyes does the chart appear to be?