SATHEE: Optics 1 Question 9

Optics 1 Question 9

9. A short linear object of length $b$ lies along the axis of a concave mirror of focal length $f$ at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to

(a) $b \frac{u - f^{1 / 2}}{f}$

(b) $b \frac{f}{u - f}$

(d) $b \frac{f^{2}}{u - f}$

Assertion and Reason

Mark your answer as

(a) If Statement I is true, Statement II is true; Statement II is the correct explanation for Statement I.

(b) If Statement I is true, Statement II is true; Statement II is not a correct explanation for Statement I.

(d) If Statement I is false; Statement II is true.

Show Answer

Answer:

Correct Answer: 9. (d)

Solution:

From the mirror formula

$\begin{aligned} \frac{1}{v} + \frac{1}{u} & = \frac{1}{f} (f = constant) \\ - v^{- 2} d v - u^{- 2} d u & = 0 \\ | d v | & = \frac{v^{2}}{u^{2}} | d u | \end{aligned}$

Here, $| d v | =$ size of image

$| d u | =$ size of object (short) lying along the axis $= b$

Further, from Eq. (i), we can find

$\frac{v^{2}}{u^{2}} = \frac{f}{u - f}$

Substituting these values in Eq. (ii), we get

Size of image $= b \frac{f}{u - f}$

$∴$ Correct option is (d).

पिछला

अगला

Optics 1 Question 9

9. A short linear object of length $b$ lies along the axis of a concave mirror of focal length $f$ at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to

Assertion and Reason

Answer:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

Optics 1 Question 9

9. A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirror. The size of the image is approximately equal to

Assertion and Reason

Answer:

इंजीनियरिंग की तैयारी

चिकित्सा तैयारी

एनसीईआरटी पुस्तकें और समाधान

महत्वपूर्ण संसाधन

अन्य संसाधन

पाठ्यक्रम

परीक्षा मंच

नमूना मॉक टेस्ट

सदस्यता

एनसीईआरटी व्यायाम वीडियो समाधान

Menu

9. A short linear object of length $b$ lies along the axis of a concave mirror of focal length $f$ at a distance $u$ from the pole of the mirror. The size of the image is approximately equal to