Physics-

#### A person is suffering from myopic defect. He is able to see clear objects placed at 15 *cm*. What type and of what focal length of lens he should use to see clearly the object placed 60 *cm* away

Physics-General

- Concave lens of 20
*cm* focal length
- Concave lens of 12
*cm* focal length
- Convex lens of 20
*cm* focal length
- Convex lens of 12
*cm* focal length

*cm*focal length*cm*focal length*cm*focal length*cm*focal length#### Answer:The correct answer is: Concave lens of 20 *cm* focal lengthFor viewing far objects, concave lenses are used and for concave lens

*u* = wants to see ; *v* = can see

so from .

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### Related Questions to study

physics-

#### The resolving limit of healthy eye is about

Resolving limit of eye is one minute (1').

#### The resolving limit of healthy eye is about

physics-General

Resolving limit of eye is one minute (1').

physics-

#### Match the List *I* with the List *II* from the combinations shown

#### Match the List *I* with the List *II* from the combinations shown

physics-General

physics-

#### 1.

2.

3.

4.

Identify the wrong description of the above figures

#### 1.

2.

3.

4.

Identify the wrong description of the above figures

physics-General

physics-

#### A ray of light is incident on an equilateral glass prism placed on a horizontal table. For minimum deviation which of the following is true

In minimum deviation position refracted ray inside the prism is parallel to the base of the prism

#### A ray of light is incident on an equilateral glass prism placed on a horizontal table. For minimum deviation which of the following is true

physics-General

In minimum deviation position refracted ray inside the prism is parallel to the base of the prism

physics-

#### In the given figure, what is the angle of prism

Angle of prism is the angle between incident and emergent surfaces.

#### In the given figure, what is the angle of prism

physics-General

Angle of prism is the angle between incident and emergent surfaces.

physics-

#### A given ray of light suffers minimum deviation in an equilateral prism *P*. Additional prisms *Q* and *R* of identical shape and material are now added to *P* as shown in the figure. The ray will suffer

As the prisms

*Q*and*R*are of the same material and have identical shape they combine to form a slab with parallel faces. Such a slab does not cause any deviation.#### A given ray of light suffers minimum deviation in an equilateral prism *P*. Additional prisms *Q* and *R* of identical shape and material are now added to *P* as shown in the figure. The ray will suffer

physics-General

As the prisms

*Q*and*R*are of the same material and have identical shape they combine to form a slab with parallel faces. Such a slab does not cause any deviation.physics-

#### A bob of mass is suspended by a massless string of length . The horizontal velocity at position is just sufficient to make it reach the point . The angle at which the speed of the bob is half of that at , satisfies

#### A bob of mass is suspended by a massless string of length . The horizontal velocity at position is just sufficient to make it reach the point . The angle at which the speed of the bob is half of that at , satisfies

physics-General

maths-

The foot of the perpendicular on the line drown from the origin is C if the line cuts the x-axis and y-axis at A and B respectively then BC : CA is

Let direction ratios of the required line be <a, b, c>

Therefore a - 2 b - 2 c = 0

And 2 b + c = 0

Þ c = - 2 b

a - 2 b + 4b = 0 Þ a = - 2 b

Therefore direction ratios of the required line are <- 2b, b, - 2b> = <2, - 1, 2>

direction cosines of the required line

=

Therefore a - 2 b - 2 c = 0

And 2 b + c = 0

Þ c = - 2 b

a - 2 b + 4b = 0 Þ a = - 2 b

Therefore direction ratios of the required line are <- 2b, b, - 2b> = <2, - 1, 2>

direction cosines of the required line

=

The foot of the perpendicular on the line drown from the origin is C if the line cuts the x-axis and y-axis at A and B respectively then BC : CA is

maths-General

Let direction ratios of the required line be <a, b, c>

Therefore a - 2 b - 2 c = 0

And 2 b + c = 0

Þ c = - 2 b

a - 2 b + 4b = 0 Þ a = - 2 b

Therefore direction ratios of the required line are <- 2b, b, - 2b> = <2, - 1, 2>

direction cosines of the required line

=

Therefore a - 2 b - 2 c = 0

And 2 b + c = 0

Þ c = - 2 b

a - 2 b + 4b = 0 Þ a = - 2 b

Therefore direction ratios of the required line are <- 2b, b, - 2b> = <2, - 1, 2>

direction cosines of the required line

=

maths-

(where a, b are integers) =

The centre of the sphere is (1, 2, –3) so if other extremity of diameter is (x

= 1, = 2, = –3

\ Required point is (0, 5, 7).

Hence (c) is the correct answer.

_{1}, y_{1}, z_{1}), then= 1, = 2, = –3

\ Required point is (0, 5, 7).

Hence (c) is the correct answer.

(where a, b are integers) =

maths-General

The centre of the sphere is (1, 2, –3) so if other extremity of diameter is (x

= 1, = 2, = –3

\ Required point is (0, 5, 7).

Hence (c) is the correct answer.

_{1}, y_{1}, z_{1}), then= 1, = 2, = –3

\ Required point is (0, 5, 7).

Hence (c) is the correct answer.

maths-

maths-General

maths-

#### ${\int}_{-\pi /4}^{\pi /4}\u200a\frac{{e}^{x}(x\mathrm{sin}x)}{{e}^{2x}-1}dx$ is equal to

Let direction cosines of straight line be l, m, n
\ 4l + m + n = 0
l – 2m + n = 0
Þ $\frac{l}{3}=\frac{m}{-3}=\frac{n}{-9}$ Þ $\frac{l}{-1}=\frac{m}{+1}=\frac{n}{3}$
\ Equation of straight line is $\frac{x-2}{-1}=\frac{y+1}{1}=\frac{z+1}{3}$.
Hence (c) is the correct choice.

#### ${\int}_{-\pi /4}^{\pi /4}\u200a\frac{{e}^{x}(x\mathrm{sin}x)}{{e}^{2x}-1}dx$ is equal to

maths-General

Let direction cosines of straight line be l, m, n
\ 4l + m + n = 0
l – 2m + n = 0
Þ $\frac{l}{3}=\frac{m}{-3}=\frac{n}{-9}$ Þ $\frac{l}{-1}=\frac{m}{+1}=\frac{n}{3}$
\ Equation of straight line is $\frac{x-2}{-1}=\frac{y+1}{1}=\frac{z+1}{3}$.
Hence (c) is the correct choice.

maths-

#### Let $f:R\to R,f\left(x\right)=\left\{\begin{array}{c}|x-[x\left]\right|,\left[x\right]\\ |x-[x+1\left]\right|,\left[x\right]\end{array}\right.$$\begin{array}{r}\text{is odd}\\ 1\text{is even where [.]}\end{array}$ denotes greatest integer function, then ${\int}_{-2}^{4}\u200af\left(x\right)dx$ is equal to

Since these two lines are intersecting so shortest distance between the lines will be 0.
Hence (c) is the correct answer.

#### Let $f:R\to R,f\left(x\right)=\left\{\begin{array}{c}|x-[x\left]\right|,\left[x\right]\\ |x-[x+1\left]\right|,\left[x\right]\end{array}\right.$$\begin{array}{r}\text{is odd}\\ 1\text{is even where [.]}\end{array}$ denotes greatest integer function, then ${\int}_{-2}^{4}\u200af\left(x\right)dx$ is equal to

maths-General

Since these two lines are intersecting so shortest distance between the lines will be 0.
Hence (c) is the correct answer.

maths-

#### The value of ${\int}_{0}^{1}\u200a|\mathrm{sin}2\pi x|\mid dx$ is equal to

Given plane y + z + 1 = 0 is parallel to x-axis as 0.1 + 1.0 + 1.0 = 0
but normal to the plane will be perpendicular to x-axis.
Hence (c) is the correct answer.

#### The value of ${\int}_{0}^{1}\u200a|\mathrm{sin}2\pi x|\mid dx$ is equal to

maths-General

Given plane y + z + 1 = 0 is parallel to x-axis as 0.1 + 1.0 + 1.0 = 0
but normal to the plane will be perpendicular to x-axis.
Hence (c) is the correct answer.

maths-

#### The value of ${\int}_{0}^{100}\u200a\left\{\sqrt{x}\right\}dx$ (where {x} is the fractional part of x) is

#### The value of ${\int}_{0}^{100}\u200a\left\{\sqrt{x}\right\}dx$ (where {x} is the fractional part of x) is

maths-General

maths-

#### The shortest distance between the two straight line$\frac{x-4/3}{2}=\frac{y+6/5}{3}=\frac{z-3/2}{4}$ and $\frac{5y+6}{8}=\frac{2z-3}{9}=\frac{3x-4}{5}$ is

#### The shortest distance between the two straight line$\frac{x-4/3}{2}=\frac{y+6/5}{3}=\frac{z-3/2}{4}$ and $\frac{5y+6}{8}=\frac{2z-3}{9}=\frac{3x-4}{5}$ is

maths-General