A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1/2 m away,

Monjur Alahi

A photocell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 1/2 m away, the number of electrons emitted by photo cathode would

(1) decrease by a factor of 4

(2) increase by a factor of 4

(3) decrease by a factor of 2

(4) increase by a factor of 2


0 like 0 dislike
1 views
Share with your friends

1 Answers

Salim Ahmed Kawsar

Call

The correct answer is (2)

l∝ 1/r2

0 like 0 dislike
1 views
Talk Doctor Online in Bissoy App
A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source

(a) must be less than 10 cm

1 Answers 1 views
A light source emits monochromatic light of wavelength 555 nm. The source consumes 100 W of electric power

Overall luminous efficiency =Total luminous flux / Power input =35x685/100 = 239.75 lumen/W

1 Answers 1 views
An illuminated object is placed on the principal axis of a converging lens so that a real image is formed on the other side of the lens. I

(b) the image will be shifted a little later than the object

1 Answers 1 views
Light from a point source falls on a small area placed perpendicular to the incident light. If the area is

The illuminance will not change.

1 Answers 1 views
The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to

The correct answer is (c) 1/r

1 Answers 1 views
A room is illuminated by an extended source. The illuminance at a particular portion of a wall can be increased by (a) moving the source

(a) moving the source (b) rotating the source (c) bringing some mirrors in proper positions (d) changing the colour of the source.

1 Answers 1 views
Mark the correct options. (a) The luminous efficiency of a monochromatic source is always greater than that of a white light source of same power.

(b) The luminous efficiency of a monochromatic source of wavelength 555 nm is always greater than that of a white light source of same power. (c) The illuminating power of a...

1 Answers 1 views
A piece of charcoal and a piece of shining steel of the same area are kept for a long time in an open lawn in bright sun.

The correct answer is (c) (d)  (c) If both are picked up by bare hands, the steel will be felt hotter than the charcoal.  (d) If the two are picked up from...

1 Answers 1 views
What is the stopping potential of a photocell, in which electrons with a maximum kinetic energy of 6eV are emitted?

Ek = eV0 => 6eV = eV0 => V0 = 6V  The stopping potential V0 = 6volt (negative)

1 Answers 1 views
"Each day is more or less the same, the morning is clear and bright with a sea breeze; as the Sun climbs high in the sky,

(b) The passage points out equatorial region.

1 Answers 1 views
X