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marissa [1.9K]
4 years ago
8

Why is a convex lens useful for starting fires

Physics
1 answer:
Anika [276]4 years ago
7 0

because if you were stuck on an island and you had a bag of of stuff and you also had a convex lens in there it could be good if u can't start a fire by rubbing to sticks instead you can use the convex lens to start a fire

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Where is the near point of an normal eye when accidentally wear a contact lens with a power of +2.0 diopters?
Lerok [7]

Answer:

The near point of an eye with power of +2 dopters, u' = - 50 cm

Given:

Power of a contact lens, P = +2.0 diopters

Solution:

To calculate the near point, we need to find the focal length of the lens which is given by:

Power, P = \frac{1}{f}

where

f = focal length

Thus

f = \frac{1}{P}

f = \frac{1}{2} = + 0.5 m

The near point of the eye is the point distant such that the image formed at this point can be seen clearly by the eye.

Now, by using lens maker formula:

\frac{1}{f} = \frac{1}{u} + \frac{1}{u'}

where

u = object distance = 25 cm = 0.25 m = near point of a normal eye

u' = image distance

Now,

\frac{1}{u'} = \frac{1}{f} - \frac{1}{u}

\frac{1}{u'} = \frac{1}{0.5} - \frac{1}{0.25}

\frac{1}{u'} = \frac{1}{f} - \frac{1}{u}

Solving the above eqn, we get:

u' = - 0.5 m = - 50 cm

7 0
3 years ago
Reflected light from a thin film of oil gives constructive interference for light with a wavelength inside the film of λfilm. By
My name is Ann [436]

Answer:D. λfilm/4

Explanation: Destructive interference is a type of wave interference which means the coming together or over-lapping of two opposing waves creating No effect or the Cancellation of the wave impact. An example of destructive wave is when Noise cancel the effect of sound from a head phone.

The film thickness will need to be increased by λfilm/4 for it to be able to give a destructive interference.

3 0
3 years ago
An object weighing 49 N is pushed across a floor by a force of 12 N. What is the acceleration of the object?
NISA [10]

Answer:

Explanation:

Given parameters:

Weight of object  = 49N

Force applied = 12N

Unknown:

Acceleration of object  = ?

Solution:

The acceleration of the object is found by dividing the force by the weight;

 Acceleration  = \frac{12}{49}   = 0.25m/s²

3 0
3 years ago
A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car’s average acceleration? A. 0.17 m/s2 B. 1.67
aliya0001 [1]
Acceleration =velocity /time
=42/7
=6
5 0
4 years ago
Read 2 more answers
The light bulb converts electrical energy into light and ____. A) chemical B) electromagnetic C) heat D) nuclear
morpeh [17]
The light bulb converts electrical energy into light and heat. 


Good luck! (:
7 0
3 years ago
Read 2 more answers
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