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3 years ago

12

A section of a sphere has a radius of curvature of 0.72 m. If this section is painted with a reflective coating on both sides, w

hat is the focal length of:

1 answer:

vaieri [72.5K]3 years ago

3 0

Answer:

The value is $f = 0.36 \ m$

Explanation:

From the question we are told that

The radius of curvature is $R = 0.72 \ m$

Generally the radius of curvature is mathematically represented as

$R = 2f$

Here $f$ is the focal length hence

$f = \frac{R}{2}$

=> $f = \frac{0.72}{2}$

=> $f = 0.36 \ m$

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A person 1.8m tall stands 0.75m from a reflecting globe in a garden.

Maru [420]

Answer:

1. The image of the person is 1.41 m, virtual and formed at the back of the surface of the globe.

2. The person's image is 3.38 m tall.

Explanation:

From the given question, object distance, u = 0.75 m, object height = 1.8 m, radius of curvature of the reflecting globe, r = 8 cm = 0.08 m.

f = $\frac{r}{2}$ = $\frac{0.08}{2}$ = 0.04 m

1. The image distance, v, can be determined by applying mirror formula:

$\frac{1}{f}$ = $\frac{1}{u}$ + $\frac{1}{v}$

$\frac{1}{0.04}$ = $\frac{1}{0.75}$ + $\frac{1}{v}$

$\frac{4}{100}$ - $\frac{75}{100}$ = $\frac{1}{v}$

$\frac{1}{v}$ = $\frac{4 - 75}{100}$

= - $\frac{71}{100}$

⇒ v = - $\frac{100}{71}$

= - 1.41 m

The image of the person is 1.41 m, virtual and formed at the back of the surface of the globe.

2. $\frac{image distance}{object distance}$ = $\frac{image height}{object height}$

$\frac{1.41}{0.75}$ = $\frac{v}{1.8}$

v = $\frac{2.538}{0.75}$

= 3.384

v = 3.38 m

The person's image is 3.38 m tall.

6 0

3 years ago

What is one characteristic of a sample of matter that indicates it is a pure substance? A) It can be separated using by a physic

snow_lady [41]

D) If the composition of a sample is fixed, the sample is a pure substance.

Explanation:

A) It can be separated by using physical means, such as filtering.

Of course using physical means as filtration or crystallization we increase the purity of a compound, however sometimes impurities may remain dissolved in the solution or they may co-precipitate with the analysed sample.

B) The components in a pure substance do not have to be in definite ratios.

If the components in a substance do not have definite rations it means the the substance is not pure, it is a mixture of something.

C) If the composition of a sample varies, the sample is a pure substance.

If the composition of a sample varies, it means that different components in the substance are changing so it is a clue that the substance is not pure.

D) If the composition of a sample is fixed, the sample is a pure substance.

If the composition of a sample is fixed, and it can be determined and proven, the substance is pure.

Learn more about:

pure substances

brainly.com/question/1339017

#learnwithBrainly

8 0

3 years ago

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The velocity of a motor bike of mass 140 kg is increased to 40m/s from 20m/s in 2 seconds. Then the force required for this is?

Liula [17]

Answer:

true blood season and answers the question of whether you are not the intended recipient you are not the intended recipient you are not the intended recipient

5 0

3 years ago

A 50-g chunk of 80 degrees C iron is dropped into a cavity in a very large block of ice at 0 degrees C. Show that 5.5 g of ice w

Alenkasestr [34]

Answer:

5.5g of ice melts when a 50g chunk of iron at 80°C is dropped into a cavity

Explanation:

The concept to solve this problem is given by Energy Transferred, the equation is given by,

$Q = mc\Delta T$

Where,

Q= Energy transferred

m = mass of water

c = specific heat capacity

$\Delta T =$ Temperature change (K or °C)

Replacing the values where mass is 50g and temperature is 80°C to 0°C we have,

$Q = mc\Delta T$

$Q = 50*0.11*(80-0)$

$Q = 440cal$

Then we can calculate the heat absorbed by m grams of ice at 0°C, then

$Q_2 = mL = 80*m$

How Q_1=Q_2, so

$80m=440$

$m=\frac{440}{80}$

$m = 5.5g$

Then 5.5g of ice melts when a 50g chunk of iron at 80°C is dropped into a cavity

7 0

4 years ago

What is the best insulator?

Aleonysh [2.5K]

Answer:

E

Explanation:

All others conduct electricity and heat.

6 0

3 years ago

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