NCERT Solutions
Board Paper Solutions
Ask & Answer
School Talk
Login
GET APP
Login
Create Account
Popular
Latest
Expert Answers
ALL
Sangeeta Jha
Subject: Physics
, asked on 22/5/18
Q.137. Assertion :- In glass, red light travels faster than blue light.
Reason :- Red light has a wavelength longer than blue.
(1) A
(2) B
(3) C
(4) D
Answer
1
Tarun Krishnan
Subject: Physics
, asked on 22/5/18
Derivation of mirror formula of a concave mirror for virtual image pls
Answer
1
Anisha Mishra
Subject: Physics
, asked on 10/5/18
The distance between an object and its doubly magnified image by a concave mirror is :
(a)3f/2
(b)2f/3
(c) 3f
(d) depends on nature of image
Answer
2
Royel Ghost
Subject: Physics
, asked on 8/5/18
please solve QUESTION number 6( b).....fast ...urgently needed...
$\mathit{Q}\mathbf{6}\mathbf{.}\mathbf{\left(}\mathit{b}\mathbf{\right)}\mathbf{}Alightraytravelsfrommedium1ofrefractiveindex{\mu}_{1}tomedium2ofrefractiveindex{\mu}_{2},where{\mu}_{2}{\mu}_{1}.Writeanexpressionforcriticalangle(i.e)ofincidence.$
Answer
1
Prithesh Dwivedi
Subject: Physics
, asked on 8/5/18
Please solve attached Question.
Q.
A circular disc of diameter d lies horizontally inside a metallic hemispherical bowl of radius 'a'. The disc is just visible to an eye looking over the edge. The bowl is now filled with a liquid of refractive index
$\mu $
. Now, the whole of the disc is just visible to the eye in the same position. Show that
$d=2a\left(\frac{{\mu}^{2}-1}{{\mu}^{2}+1}\right)$
Answer
1
Prithesh Dwivedi
Subject: Physics
, asked on 7/5/18
Pls solve attached Q:13.:
A cylindrical vessel, whose diameter and height both are equal to 30 crn, is placed on a horizontal surface and a small particle P is placed in it at a distance of 5.0 cm from the centre. An eye is placed at a position such that the edge of the bottom is just visible. The particle P is in the plane of drawing. Up to what minimum height should water be poured in the vessel to make the particle P visible?
Answer
1
Surbhi Singh
Subject: Physics
, asked on 7/5/18
please answer these two ques asap
19.
A barometer tube reads 75 cm of Hg. If tube is gradually inclined at an angle of 30
$\xb0$
$\xb0$
with horizontal, keeping the open end in the mercury container, then find the length of column in the barometer tube
(1) 86.7 cm
(2) 150 cm
(3) 75 cm
(4) 92.5 cm
20.
A metallic sphere weighing 3 kg in air is held by a string so as to be completely immersed in a liquid of relative density 0.8. The relative density of metallic is 10. The tension in the string is
(1) 18.7 N
(2) 42.5 N
(3) 32.7 N
(4) 27.6 N
Answer
1
Haripriya
Subject: Physics
, asked on 4/5/18
Please solve this ...
Q.4. An equilateral prism deviates a ray of light through 23
$\xb0$
for two angles of incidence, which differs by 23
$\xb0$
. The refractive index of prism is
a)
$\frac{\sqrt{33}}{5}$
b)
$\frac{\sqrt{43}}{5}$
c) 1.5
d)
$\frac{4}{3}$
Answer
1
Haripriya
Subject: Physics
, asked on 4/5/18
Please solve these two questions..
4
. An equilateral prism deviates a ray of light through 23
$\xb0$
for two angles of incidence, which differs by
23
$\xb0$
. The refractive index of prism is
$a)\frac{\sqrt{33}}{5}b)\frac{\sqrt{43}}{5}c)1.5d)\frac{4}{3}$
5.
The plane side of a planoconvex lens is silvered and the lens then acts like a concave mirror of 30cm focal length. The refractive index of lens is 1.5. What is the radius of curvature of this lens?
a) 20 cm b) 30 cm c) 40 cm d) 25 cm
Answer
1
Jeneeta Eliza John
Subject: Physics
, asked on 1/5/18
Question no.18. Ans(2)
$Planesurfaceofplanoconvexlensofrefractiveindex\text{'}\mu \text{'}andradiusofcurvatureRissilveredandobjectisplacedinfrontofcurvedfacethenfocallengthoflensis\phantom{\rule{0ex}{0ex}}\left(1\right)\frac{R}{2(\mu -1)}\phantom{\rule{0ex}{0ex}}\left(2\right)\frac{-R}{2(\mu -1)}\phantom{\rule{0ex}{0ex}}\left(3\right)\frac{2(\mu -1)}{R}\phantom{\rule{0ex}{0ex}}\left(4\right)\frac{-2(\mu -1)}{R}$
Answer
1
Royel Ghost
Subject: Physics
, asked on 30/4/18
make me understand the principle of reversibility of light......pls.....fast need urgently...
${\mathrm{\mu}}_{\mathrm{g}}\times \mathrm{sin}{\mathrm{i}}_{2}={\mathrm{\mu}}_{\mathrm{a}}\mathrm{sin}{\mathrm{r}}_{2}\phantom{\rule{0ex}{0ex}}\frac{{\mathrm{\mu}}_{\mathrm{a}}}{{\mathrm{\mu}}_{\mathrm{g}}}=\frac{\mathrm{sin}{\mathrm{i}}_{2}}{\mathrm{sin}{\mathrm{r}}_{2}}={\mathrm{g\mu}}_{\mathrm{a}}.....\left(2\right)$
According to the
principle of reversibility of light, when final path of a ray of light after any number of refractions and refractions is reversed, the ray retraces its entire path.
Imagine a plane mirror P held normal to MN so that on reflection from mirror, path MN is reversed. The ray would retrace its entire path. For the reversed ray, application of Snell's law at M gives
Answer
1
Sandra Saju
Subject: Physics
, asked on 29/4/18
A concave mirror of focal length 15cm forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be. (i) 22.5 cm. (ii) 7.5 cm. ( iii) 30 cm. (iv) 45 cm.
Answer
1
Sandra Saju
Subject: Physics
, asked on 28/4/18
Two identical glass(Ng=3/2) equiconvex lenses of focal length f are kept in contact. Thr space between the two lenses is filled with water (Nw=4/3). The focal length of the combination is. A)F B)f/2 C)4f/3 D)3f/4
Answer
1
Sandra Saju
Subject: Physics
, asked on 28/4/18
A convex lens of focal length f produces an image 1/n times that of the size of the object. The distance of the object from the lens is. (i) f/n. (ii) nf ( iii) (n-1)f (iv)(n+1)f
Answer
1
Sandra Saju
Subject: Physics
, asked on 28/4/18
A concave mirror of focal length 15 cm forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be. (i) 22.5 cm. (ii) 7.5 cm. (iii) 30 cm. (iv) 45cm
Answer
1
1
2
3
4
5
Next
What are you looking for?

Reason :- Red light has a wavelength longer than blue.

(1) A

(2) B

(3) C

(4) D

(a)3f/2

(b)2f/3

(c) 3f

(d) depends on nature of image

$\mathit{Q}\mathbf{6}\mathbf{.}\mathbf{\left(}\mathit{b}\mathbf{\right)}\mathbf{}Alightraytravelsfrommedium1ofrefractiveindex{\mu}_{1}tomedium2ofrefractiveindex{\mu}_{2},where{\mu}_{2}{\mu}_{1}.Writeanexpressionforcriticalangle(i.e)ofincidence.$

Q.A circular disc of diameter d lies horizontally inside a metallic hemispherical bowl of radius 'a'. The disc is just visible to an eye looking over the edge. The bowl is now filled with a liquid of refractive index $\mu $. Now, the whole of the disc is just visible to the eye in the same position. Show that $d=2a\left(\frac{{\mu}^{2}-1}{{\mu}^{2}+1}\right)$A cylindrical vessel, whose diameter and height both are equal to 30 crn, is placed on a horizontal surface and a small particle P is placed in it at a distance of 5.0 cm from the centre. An eye is placed at a position such that the edge of the bottom is just visible. The particle P is in the plane of drawing. Up to what minimum height should water be poured in the vessel to make the particle P visible?

19.A barometer tube reads 75 cm of Hg. If tube is gradually inclined at an angle of 30$\xb0$$\xb0$ with horizontal, keeping the open end in the mercury container, then find the length of column in the barometer tube(1) 86.7 cm

(2) 150 cm

(3) 75 cm

(4) 92.5 cm

20.A metallic sphere weighing 3 kg in air is held by a string so as to be completely immersed in a liquid of relative density 0.8. The relative density of metallic is 10. The tension in the string is(1) 18.7 N

(2) 42.5 N

(3) 32.7 N

(4) 27.6 N

Q.4. An equilateral prism deviates a ray of light through 23$\xb0$ for two angles of incidence, which differs by 23$\xb0$. The refractive index of prism is

a) $\frac{\sqrt{33}}{5}$

b) $\frac{\sqrt{43}}{5}$

c) 1.5

d) $\frac{4}{3}$

4. An equilateral prism deviates a ray of light through 23$\xb0$ for two angles of incidence, which differs by23$\xb0$. The refractive index of prism is

$a)\frac{\sqrt{33}}{5}b)\frac{\sqrt{43}}{5}c)1.5d)\frac{4}{3}$

5.The plane side of a planoconvex lens is silvered and the lens then acts like a concave mirror of 30cm focal length. The refractive index of lens is 1.5. What is the radius of curvature of this lens?a) 20 cm b) 30 cm c) 40 cm d) 25 cm

$Planesurfaceofplanoconvexlensofrefractiveindex\text{'}\mu \text{'}andradiusofcurvatureRissilveredandobjectisplacedinfrontofcurvedfacethenfocallengthoflensis\phantom{\rule{0ex}{0ex}}\left(1\right)\frac{R}{2(\mu -1)}\phantom{\rule{0ex}{0ex}}\left(2\right)\frac{-R}{2(\mu -1)}\phantom{\rule{0ex}{0ex}}\left(3\right)\frac{2(\mu -1)}{R}\phantom{\rule{0ex}{0ex}}\left(4\right)\frac{-2(\mu -1)}{R}$

${\mathrm{\mu}}_{\mathrm{g}}\times \mathrm{sin}{\mathrm{i}}_{2}={\mathrm{\mu}}_{\mathrm{a}}\mathrm{sin}{\mathrm{r}}_{2}\phantom{\rule{0ex}{0ex}}\frac{{\mathrm{\mu}}_{\mathrm{a}}}{{\mathrm{\mu}}_{\mathrm{g}}}=\frac{\mathrm{sin}{\mathrm{i}}_{2}}{\mathrm{sin}{\mathrm{r}}_{2}}={\mathrm{g\mu}}_{\mathrm{a}}.....\left(2\right)$

According to the

principle of reversibility of light, when final path of a ray of light after any number of refractions and refractions is reversed, the ray retraces its entire path.Imagine a plane mirror P held normal to MN so that on reflection from mirror, path MN is reversed. The ray would retrace its entire path. For the reversed ray, application of Snell's law at M gives