Physics-

General

Easy

### Question

#### The distance between a point source of light and a screen which is 60 *cm* is increased to 180 *cm*. The intensity on the screen as compared with the original intensity will be

- (1/9) times
- (1/3) times
- 3 times
- 9 times

#### The correct answer is: (1/9) times

## Book A Free Demo

+91

Grade*

Select Grade

### Related Questions to study

Maths-

The pole of the straight line 9x + y – 28 = 0 with respect to the circle is

The pole of the straight line 9x + y – 28 = 0 with respect to the circle is

Maths-General

physics-

#### Three rods of equal length are joined to form an equilateral triangle O is the mid point of Distance remains same for small change in temperature. Coefficient of linear expansion for and is same, but that for is Then

Neglecting and

#### Three rods of equal length are joined to form an equilateral triangle O is the mid point of Distance remains same for small change in temperature. Coefficient of linear expansion for and is same, but that for is Then

physics-General

Neglecting and

physics-

#### A point source causes photoelectric effect from a small metal plate Which of the following curves may represent the saturation photocurrent as a function of the distance between the source and the metal?

#### A point source causes photoelectric effect from a small metal plate Which of the following curves may represent the saturation photocurrent as a function of the distance between the source and the metal?

physics-General

physics-

#### One of the following figures respesents the variation of particle momentum with associated de Broglie wavelength

a)

b)

c)

#### One of the following figures respesents the variation of particle momentum with associated de Broglie wavelength

a)

b)

c)

physics-General

physics-

#### Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

According to Newton’s law of cooling, rate of cooling is given by

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

#### Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

physics-General

According to Newton’s law of cooling, rate of cooling is given by

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

physics-

#### Which of the curves in figure represents the relation between Celsius and Fahrenheit temperatures

Hence graph between and will be a straight line with positive slope and negative intercept

#### Which of the curves in figure represents the relation between Celsius and Fahrenheit temperatures

physics-General

Hence graph between and will be a straight line with positive slope and negative intercept

Maths-

The area of circle centred at (1, 2) and passing through (4, 6) is

The area of circle centred at (1, 2) and passing through (4, 6) is

Maths-General

physics-

#### Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities and . The points and are maintained at different temperatures for the heat to flow at the same rate along and then which of the following options is correct

The given arrangement of rods can be redrawn as follows

It is given that

It is given that

#### Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities and . The points and are maintained at different temperatures for the heat to flow at the same rate along and then which of the following options is correct

physics-General

The given arrangement of rods can be redrawn as follows

It is given that

It is given that

physics-

#### In the following diagram if then

#### In the following diagram if then

physics-General

physics-

#### The maximum kinetic energy (E_{k} ) of emitted photoelectrons against frequency v of incident radiation is plotted as shown in fig The slope of the graph is equal to

#### The maximum kinetic energy (E_{k} ) of emitted photoelectrons against frequency v of incident radiation is plotted as shown in fig The slope of the graph is equal to

physics-General

maths-

In centre of the triangle formed by the lines y = x, y = 3x and y = 8 – 3x is

In centre of the triangle formed by the lines y = x, y = 3x and y = 8 – 3x is

maths-General

physics-

#### A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

#### A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

physics-General

physics-

#### Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

Efficiency of light source

..... (i)

and ..... (ii)

From equation (i) and (ii)

.

..... (i)

and ..... (ii)

From equation (i) and (ii)

.

#### Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

physics-General

Efficiency of light source

..... (i)

and ..... (ii)

From equation (i) and (ii)

.

..... (i)

and ..... (ii)

From equation (i) and (ii)

.

physics-

#### Lux is equal to

#### Lux is equal to

physics-General

physics-

#### A 60 *watt* bulb is hung over the center of a table at a height of 3 *m*. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is

#### A 60 *watt* bulb is hung over the center of a table at a height of 3 *m*. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is

physics-General