Single Choice

The focal length of a concave mirror is $$f$$ and the distance from the object to the principal focus is $$x$$. The ratio of the size of the image to the size of the object is :

A$$\dfrac{f+x}{f}$$
B$$\dfrac{f}{x}$$
Correct Answer
C$$\sqrt{\dfrac{f}{x}}$$
D$$\dfrac{f^2}{x^2}$$

Solution

As we know,
$$\dfrac{I}{O}=\dfrac{f}{f-u};$$ where $$u=f+x$$ $$\therefore \dfrac{I}{O}=-\dfrac{f}{x}$$

SIMILAR QUESTIONS

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The focal length of converging lens are $$ { f }_{ v }\ and\ { f }_{ r }$$ for violet and red light respectively,then

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Which of the following quantities increase when wavelength is increased? Consider only the magnitudes.

Optics

Which of the following quantities related to a lens depend on the wavelength or wavelength of the incident light?

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A thin converging lens is placed between an object and a screen whose positions are fixed. There are two positions of the lens at which the sharp image of the object is formed on the screen. Find the transverse dimension of the object if at one position of the lens the image dimension equals $$ h^{\prime}=2.0 \mathrm{mm} $$ and at the other, $$ h^{\prime \prime}=4.5 \mathrm{mm} $$

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A Galilean telescope of 10-fold magnification has a length of $$ 45 \mathrm{cm} $$ when adjusted to infinity. Determine: (a) the focal lengths of the telescope's objective and ocular;

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In order top obtain a real image of magnification $$2$$ bring a converging lens of focal length $$20cm$$, where should be an object be placed

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Light of wavelength is $$7200\ \overset {o}{A}$$ in air. It has a wavelength in glass $$(\mu =1.5)$$ equal to

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Which of the following is not a correct statement.

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Focal length of a converging lens air in $$R$$. If it is dipped in water of refractive index $$1.33$$, then its focal length will be around (Refractive index of lens material is $$1.5$$)

Optics

The focal length of a convex lens depends upon

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