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Ray Optics

282912 The minimum intensity of light to be detected by human eye is $10^{- 10} W / m^{2}$ . The number of photon of wavelength $5.6 \times 10^{- 7} m$ entering the eye, with pupil area $10^{- 6} m^{2}$ , per second for vision will be nearly

1 100

2 200

3 300

4 400

Explanation:

C: Given,
Intensity $(I) = 10^{- 10} W / m^{2}$
Wavelength $(λ) = 5.6 \times 10^{- 7} m$
Area of pupil $(A) = 10^{- 6} m^{2}$
We know that-
Radiation power $(P) = I \times A$
$\begin{array}{r} \frac{nhc}{t λ} = I \times A \\ \frac{n}{t} = \frac{IA λ}{hc} \\ \frac{n}{t} = \frac{10^{- 10} \times 10^{- 6} \times 5.6 \times 10^{- 7}}{6.67 \times 10^{- 34} \times 3 \times 10^{8}} = 279.86 \approx 300 \\ \frac{n}{t} = 300 \end{array}$
Where, $h =$ Plank's constant $(6.67 \times 10^{- 34} J$ -s $)$
$\begin{array}{r} h = Plank's constant (6.67 \times 10^{- 34} J - s) \\ c = 3 \times 10^{8} m / s \\ \frac{n}{t} = number of photons entering eye per second \end{array}$

Manipal UGET-2014

Ray Optics

282913 An observer loop at a tree of height $15 m$ with a telescope of magnifying power 10 . To him the tree appears

1 10 times taller

2 15 times taller

3 10 times nearer

4 15 times nearer

Explanation:

C: Given,
Height of tree $(h) = 15 m$
Magnifying power $(m) = 20$
The angle subtended at the eye becomes 10 times larger, this happens only when the tree appears 10 times nearer

Manipal UGET-2013

Ray Optics

282914 When the wavelength of sound changes from 1 $m$ to $1.01 m$ , the number of beats heard are 4 . The velocity of sound is

1

404 m / s

2

4.04 m / s

3

414 m / s

4

400 m / s

Explanation:

A: Given, $λ_{1} = 1 m$ and $λ_{2} = 1.01 m$ beats $(b) = 4$
No. of beats $(b) = v (\frac{1}{λ_{1}} - \frac{1}{λ_{2}})$
$4 = v (\frac{1}{1} - \frac{1}{1.01})$
$v = \frac{4}{(1 - \frac{1}{1.01})}$
$v = 404 m / s$

Manipal UGET-2010

Ray Optics

282929 Which of the statements is incorrect about the simple microscope?

1 Biology students use to see the slides.

2 It is not used for magnification of an object at far away from the observer.

3 Magnification of microscope is inversely proportional to the least distance of distinct vision.

4 A convex lens of microscope with sorter focal length yields higher magnification.

Explanation:

C: Magnification,
$m = 1 + \frac{D}{f}$
Where, $D =$ least distance of distinct vision

UPSEE - 2016

Ray Optics

282930 The resolving power of telescope depends on

1 focal length of eye lens

2 focal length of objective lens

3 length of the telescope

4 diameter of the objective lens

Explanation:

D: Resolving power $α = \frac{d}{1.22 λ}$
Where, $d =$ diameter of objective lens.

UPSEE - 2013

Ray Optics

282912 The minimum intensity of light to be detected by human eye is $10^{- 10} W / m^{2}$ . The number of photon of wavelength $5.6 \times 10^{- 7} m$ entering the eye, with pupil area $10^{- 6} m^{2}$ , per second for vision will be nearly

1 100

2 200

3 300

4 400

Explanation:

C: Given,
Intensity $(I) = 10^{- 10} W / m^{2}$
Wavelength $(λ) = 5.6 \times 10^{- 7} m$
Area of pupil $(A) = 10^{- 6} m^{2}$
We know that-
Radiation power $(P) = I \times A$
$\begin{array}{r} \frac{nhc}{t λ} = I \times A \\ \frac{n}{t} = \frac{IA λ}{hc} \\ \frac{n}{t} = \frac{10^{- 10} \times 10^{- 6} \times 5.6 \times 10^{- 7}}{6.67 \times 10^{- 34} \times 3 \times 10^{8}} = 279.86 \approx 300 \\ \frac{n}{t} = 300 \end{array}$
Where, $h =$ Plank's constant $(6.67 \times 10^{- 34} J$ -s $)$
$\begin{array}{r} h = Plank's constant (6.67 \times 10^{- 34} J - s) \\ c = 3 \times 10^{8} m / s \\ \frac{n}{t} = number of photons entering eye per second \end{array}$

Manipal UGET-2014

Ray Optics

282913 An observer loop at a tree of height $15 m$ with a telescope of magnifying power 10 . To him the tree appears

1 10 times taller

2 15 times taller

3 10 times nearer

4 15 times nearer

Explanation:

C: Given,
Height of tree $(h) = 15 m$
Magnifying power $(m) = 20$
The angle subtended at the eye becomes 10 times larger, this happens only when the tree appears 10 times nearer

Manipal UGET-2013

Ray Optics

282914 When the wavelength of sound changes from 1 $m$ to $1.01 m$ , the number of beats heard are 4 . The velocity of sound is

1

404 m / s

2

4.04 m / s

3

414 m / s

4

400 m / s

Explanation:

A: Given, $λ_{1} = 1 m$ and $λ_{2} = 1.01 m$ beats $(b) = 4$
No. of beats $(b) = v (\frac{1}{λ_{1}} - \frac{1}{λ_{2}})$
$4 = v (\frac{1}{1} - \frac{1}{1.01})$
$v = \frac{4}{(1 - \frac{1}{1.01})}$
$v = 404 m / s$

Manipal UGET-2010

Ray Optics

282929 Which of the statements is incorrect about the simple microscope?

1 Biology students use to see the slides.

2 It is not used for magnification of an object at far away from the observer.

3 Magnification of microscope is inversely proportional to the least distance of distinct vision.

4 A convex lens of microscope with sorter focal length yields higher magnification.

Explanation:

C: Magnification,
$m = 1 + \frac{D}{f}$
Where, $D =$ least distance of distinct vision

UPSEE - 2016

Ray Optics

282930 The resolving power of telescope depends on

1 focal length of eye lens

2 focal length of objective lens

3 length of the telescope

4 diameter of the objective lens

Explanation:

D: Resolving power $α = \frac{d}{1.22 λ}$
Where, $d =$ diameter of objective lens.

UPSEE - 2013

Ray Optics

282912 The minimum intensity of light to be detected by human eye is $10^{- 10} W / m^{2}$ . The number of photon of wavelength $5.6 \times 10^{- 7} m$ entering the eye, with pupil area $10^{- 6} m^{2}$ , per second for vision will be nearly

1 100

2 200

3 300

4 400

Explanation:

C: Given,
Intensity $(I) = 10^{- 10} W / m^{2}$
Wavelength $(λ) = 5.6 \times 10^{- 7} m$
Area of pupil $(A) = 10^{- 6} m^{2}$
We know that-
Radiation power $(P) = I \times A$
$\begin{array}{r} \frac{nhc}{t λ} = I \times A \\ \frac{n}{t} = \frac{IA λ}{hc} \\ \frac{n}{t} = \frac{10^{- 10} \times 10^{- 6} \times 5.6 \times 10^{- 7}}{6.67 \times 10^{- 34} \times 3 \times 10^{8}} = 279.86 \approx 300 \\ \frac{n}{t} = 300 \end{array}$
Where, $h =$ Plank's constant $(6.67 \times 10^{- 34} J$ -s $)$
$\begin{array}{r} h = Plank's constant (6.67 \times 10^{- 34} J - s) \\ c = 3 \times 10^{8} m / s \\ \frac{n}{t} = number of photons entering eye per second \end{array}$

Manipal UGET-2014

Ray Optics

282913 An observer loop at a tree of height $15 m$ with a telescope of magnifying power 10 . To him the tree appears

1 10 times taller

2 15 times taller

3 10 times nearer

4 15 times nearer

Explanation:

C: Given,
Height of tree $(h) = 15 m$
Magnifying power $(m) = 20$
The angle subtended at the eye becomes 10 times larger, this happens only when the tree appears 10 times nearer

Manipal UGET-2013

Ray Optics

282914 When the wavelength of sound changes from 1 $m$ to $1.01 m$ , the number of beats heard are 4 . The velocity of sound is

1

404 m / s

2

4.04 m / s

3

414 m / s

4

400 m / s

Explanation:

A: Given, $λ_{1} = 1 m$ and $λ_{2} = 1.01 m$ beats $(b) = 4$
No. of beats $(b) = v (\frac{1}{λ_{1}} - \frac{1}{λ_{2}})$
$4 = v (\frac{1}{1} - \frac{1}{1.01})$
$v = \frac{4}{(1 - \frac{1}{1.01})}$
$v = 404 m / s$

Manipal UGET-2010

Ray Optics

282929 Which of the statements is incorrect about the simple microscope?

1 Biology students use to see the slides.

2 It is not used for magnification of an object at far away from the observer.

3 Magnification of microscope is inversely proportional to the least distance of distinct vision.

4 A convex lens of microscope with sorter focal length yields higher magnification.

Explanation:

C: Magnification,
$m = 1 + \frac{D}{f}$
Where, $D =$ least distance of distinct vision

UPSEE - 2016

Ray Optics

282930 The resolving power of telescope depends on

1 focal length of eye lens

2 focal length of objective lens

3 length of the telescope

4 diameter of the objective lens

Explanation:

D: Resolving power $α = \frac{d}{1.22 λ}$
Where, $d =$ diameter of objective lens.

UPSEE - 2013

Ray Optics

282912 The minimum intensity of light to be detected by human eye is $10^{- 10} W / m^{2}$ . The number of photon of wavelength $5.6 \times 10^{- 7} m$ entering the eye, with pupil area $10^{- 6} m^{2}$ , per second for vision will be nearly

1 100

2 200

3 300

4 400

Explanation:

C: Given,
Intensity $(I) = 10^{- 10} W / m^{2}$
Wavelength $(λ) = 5.6 \times 10^{- 7} m$
Area of pupil $(A) = 10^{- 6} m^{2}$
We know that-
Radiation power $(P) = I \times A$
$\begin{array}{r} \frac{nhc}{t λ} = I \times A \\ \frac{n}{t} = \frac{IA λ}{hc} \\ \frac{n}{t} = \frac{10^{- 10} \times 10^{- 6} \times 5.6 \times 10^{- 7}}{6.67 \times 10^{- 34} \times 3 \times 10^{8}} = 279.86 \approx 300 \\ \frac{n}{t} = 300 \end{array}$
Where, $h =$ Plank's constant $(6.67 \times 10^{- 34} J$ -s $)$
$\begin{array}{r} h = Plank's constant (6.67 \times 10^{- 34} J - s) \\ c = 3 \times 10^{8} m / s \\ \frac{n}{t} = number of photons entering eye per second \end{array}$

Manipal UGET-2014

Ray Optics

282913 An observer loop at a tree of height $15 m$ with a telescope of magnifying power 10 . To him the tree appears

1 10 times taller

2 15 times taller

3 10 times nearer

4 15 times nearer

Explanation:

C: Given,
Height of tree $(h) = 15 m$
Magnifying power $(m) = 20$
The angle subtended at the eye becomes 10 times larger, this happens only when the tree appears 10 times nearer

Manipal UGET-2013

Ray Optics

282914 When the wavelength of sound changes from 1 $m$ to $1.01 m$ , the number of beats heard are 4 . The velocity of sound is

1

404 m / s

2

4.04 m / s

3

414 m / s

4

400 m / s

Explanation:

A: Given, $λ_{1} = 1 m$ and $λ_{2} = 1.01 m$ beats $(b) = 4$
No. of beats $(b) = v (\frac{1}{λ_{1}} - \frac{1}{λ_{2}})$
$4 = v (\frac{1}{1} - \frac{1}{1.01})$
$v = \frac{4}{(1 - \frac{1}{1.01})}$
$v = 404 m / s$

Manipal UGET-2010

Ray Optics

282929 Which of the statements is incorrect about the simple microscope?

1 Biology students use to see the slides.

2 It is not used for magnification of an object at far away from the observer.

3 Magnification of microscope is inversely proportional to the least distance of distinct vision.

4 A convex lens of microscope with sorter focal length yields higher magnification.

Explanation:

C: Magnification,
$m = 1 + \frac{D}{f}$
Where, $D =$ least distance of distinct vision

UPSEE - 2016

Ray Optics

282930 The resolving power of telescope depends on

1 focal length of eye lens

2 focal length of objective lens

3 length of the telescope

4 diameter of the objective lens

Explanation:

D: Resolving power $α = \frac{d}{1.22 λ}$
Where, $d =$ diameter of objective lens.

UPSEE - 2013

Ray Optics

282912 The minimum intensity of light to be detected by human eye is $10^{- 10} W / m^{2}$ . The number of photon of wavelength $5.6 \times 10^{- 7} m$ entering the eye, with pupil area $10^{- 6} m^{2}$ , per second for vision will be nearly

1 100

2 200

3 300

4 400

Explanation:

C: Given,
Intensity $(I) = 10^{- 10} W / m^{2}$
Wavelength $(λ) = 5.6 \times 10^{- 7} m$
Area of pupil $(A) = 10^{- 6} m^{2}$
We know that-
Radiation power $(P) = I \times A$
$\begin{array}{r} \frac{nhc}{t λ} = I \times A \\ \frac{n}{t} = \frac{IA λ}{hc} \\ \frac{n}{t} = \frac{10^{- 10} \times 10^{- 6} \times 5.6 \times 10^{- 7}}{6.67 \times 10^{- 34} \times 3 \times 10^{8}} = 279.86 \approx 300 \\ \frac{n}{t} = 300 \end{array}$
Where, $h =$ Plank's constant $(6.67 \times 10^{- 34} J$ -s $)$
$\begin{array}{r} h = Plank's constant (6.67 \times 10^{- 34} J - s) \\ c = 3 \times 10^{8} m / s \\ \frac{n}{t} = number of photons entering eye per second \end{array}$

Manipal UGET-2014

Ray Optics

282913 An observer loop at a tree of height $15 m$ with a telescope of magnifying power 10 . To him the tree appears

1 10 times taller

2 15 times taller

3 10 times nearer

4 15 times nearer

Explanation:

C: Given,
Height of tree $(h) = 15 m$
Magnifying power $(m) = 20$
The angle subtended at the eye becomes 10 times larger, this happens only when the tree appears 10 times nearer

Manipal UGET-2013

Ray Optics

282914 When the wavelength of sound changes from 1 $m$ to $1.01 m$ , the number of beats heard are 4 . The velocity of sound is

1

404 m / s

2

4.04 m / s

3

414 m / s

4

400 m / s

Explanation:

A: Given, $λ_{1} = 1 m$ and $λ_{2} = 1.01 m$ beats $(b) = 4$
No. of beats $(b) = v (\frac{1}{λ_{1}} - \frac{1}{λ_{2}})$
$4 = v (\frac{1}{1} - \frac{1}{1.01})$
$v = \frac{4}{(1 - \frac{1}{1.01})}$
$v = 404 m / s$

Manipal UGET-2010

Ray Optics

282929 Which of the statements is incorrect about the simple microscope?

1 Biology students use to see the slides.

2 It is not used for magnification of an object at far away from the observer.

3 Magnification of microscope is inversely proportional to the least distance of distinct vision.

4 A convex lens of microscope with sorter focal length yields higher magnification.

Explanation:

C: Magnification,
$m = 1 + \frac{D}{f}$
Where, $D =$ least distance of distinct vision

UPSEE - 2016

Ray Optics

282930 The resolving power of telescope depends on

1 focal length of eye lens

2 focal length of objective lens

3 length of the telescope

4 diameter of the objective lens

Explanation:

D: Resolving power $α = \frac{d}{1.22 λ}$
Where, $d =$ diameter of objective lens.

UPSEE - 2013

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