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2 years ago

Which of the following describes a chemical change?

Physics

1 answer:

Thepotemich [5.8K]2 years ago

4 0

Answer:

D. Burning paper

Explanation:

physical change is just changing the way it looks

chemical change is changing the properties of the object or thing

melting ice is just changing the way it looks it still has the same atoms and elements.

when you burn something it will change the properties of the atoms in the object

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The bae chart shows the percentage of adults in the U.S. living with certain heart disease risk factors. Which conclusion can be

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3 years ago

For a certain optical medium the speed of light varies from a low value of 1.90 × 10 8 m/s for violet light to a high value of 2

Dmitry_Shevchenko [17]

Answer:

a. The refractive index ranges from 1.5 - 1.56

b. 18.7° for violet light and 19.5° for red light.

c. 33.7° for violet light and 35.3° for red light.

Explanation:

a. The refractive index of an object is the ratio of the speed of light in a vacuum and the speed of light in the object.

Mathematically,

$n = \frac{c}{v}$

The speed of violet light in the object is $1.9 * 10^8 m/s$ .

The speed of red light in the object is $2 * 10^8 m/s$

Hence, the refractive index for violet light is:

$n = \frac{3 * 10^8 }{1.9 * 10^8} \\\\n = 1.56$

and for red light, it is:

$n = \frac{3 * 10^8 }{2 * 10^8} \\\\n = 1.5$

Hence, the refractive index ranges from 1.5 - 1.56.

b. The refractive index is also the ratio of the sine of the angle of incidence to the sine of the angle of refraction.

$n = \frac{sin(i)}{sin(r)}$

The angle of incidence is 30°.

The angle of refraction for violet light will be:

$1.56 = \frac{sin(30)}{sin(r)}\\ \\sin(r) = \frac{sin(30)}{1.56} = \frac{0.5}{1.56} \\\\sin(r) = 0.3205\\\\r = 18.7^o$

And the angle of refraction for red light will be:

$1.5 = \frac{sin(30)}{sin(r)}\\ \\sin(r) = \frac{sin(30)}{1.5} = \frac{0.5}{1.5} \\\\sin(r) = 0.3333\\\\r = 19.5^o$

The angle of refraction for red light is larger than that of violet light when the angle of incidence is 30°.

c. The angle of incidence is 60°.

The angle of refraction for violet light will be:

$1.56 = \frac{sin(60)}{sin(r)}\\ \\sin(r) = \frac{sin(60)}{1.56} = \frac{0.8660}{1.56} \\\\sin(r) = 0.5551\\\\r = 33.7^o$

And the angle of refraction for red light will be:

$1.5 = \frac{sin(60)}{sin(r)}\\ \\sin(r) = \frac{sin(60)}{1.5} = \frac{0.8660}{1.5} \\\\sin(r) = 0.5773\\\\r = 35.3^o$

The angle of refraction for red light is still larger than that of violet light when the angle of incidence is 60°.

6 0

3 years ago

List 5 differences between a compound and an element.

Anuta_ua [19.1K]

Answer:

1.An element consists of the same kind of atoms while a compound is composed of different kinds of atoms.

2.A monoatomic element cannot be split up physically or chemically but a compound can be split up into new substances by chemical means.

3.Only limited number of elements are known in an element whiles number of known compounds are quite large.

4.The property of an element is the property of the atom whiles the property of a compound is quite different from that of it's constituents.

5 . Elements are represented by symbols and numbers.for example Sodium is represented by Na whiles compounds are represented by their chemical formula.for example,Salt is represented by the formula NaCl.

5 0

3 years ago

The strength of the electric field at a certain distance from a point charge is represented by e. What is the strength of the el

Masteriza [31]

Answer:

At twice the distance, the strength of the field is e/4

Explanation:

F = the strength of an electric field.

F is inversely proportional to the squared distance from the point charge.

mathematically,

F = k(e/d²)

hence, if d is doubled,keeping other forms constant

F = e/4,

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3 years ago

How much work does a 30W engine do if it operates for 40 seconds

swat32

Given that :

Power (P) = 30 W ,

time (t) = 40 s,

Work = ?

we know that, power is defined as rate of doing work

Power = Work ÷ time

=> Work = Power × time

= 30 × 40

7 0

3 years ago