When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a distance of 10 cm from the mirror. If the object is moved with a speed of 9 cms -1, the speed (in cms -1 ) with which image moves at that instant is .

Question

When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a distance of 10 cm from the mirror. If the object is moved with a speed of 9 cms -1, the speed (in cms -1 ) with which image moves at that instant is . (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

|((dv/dt))|=|(v2/42)||(du/dt)|=((10/30))2×9=1 m /s

Q. When an object is kept at a distance of $30 c m$ from a concave mirror, the image is formed at a distance of $10 c m$ from the mirror. If the object is moved with a speed of $9 c m s^{- 1}$ , the speed (in $c m s^{- 1})$ with which image moves at that instant is _______.

$∣ ∣ (\frac{d v}{d t}) ∣ ∣ = ∣ ∣ \frac{v ^{2}}{4 ^{2}} ∣ ∣ ∣ ∣ \frac{d u}{d t} ∣ ∣ = (\frac{10}{30}) 2 \times 9 = 1 m / s$

Q. When an object is kept at a distance of 30cm from a concave mirror, the image is formed at a distance of 10cm from the mirror. If the object is moved with a speed of 9cms−1, the speed (in cms−1) with which image moves at that instant is _______.

∣∣​(dtdv​)∣∣​=∣∣​42v2​∣∣​∣∣​dtdu​∣∣​=(3010​)2×9=1m/s

Q. When an object is kept at a distance of $30 c m$ from a concave mirror, the image is formed at a distance of $10 c m$ from the mirror. If the object is moved with a speed of $9 c m s^{- 1}$ , the speed (in $c m s^{- 1})$ with which image moves at that instant is _______.

$∣ ∣ (\frac{d v}{d t}) ∣ ∣ = ∣ ∣ \frac{v ^{2}}{4 ^{2}} ∣ ∣ ∣ ∣ \frac{d u}{d t} ∣ ∣ = (\frac{10}{30}) 2 \times 9 = 1 m / s$