Boron Group
elements have three valence electrons and are fairly reactive. All of them are solids at room temperature. Boron is a very hard, black metalloid with a high melting point.
Answer:
R2 = 300 Ohms
Explanation:
Let the two resistors be R1 and R2 respectively.
RT is the total equivalent resistance.
Given the following data;
R1 = 100 Ohms
RT = 75 Ohms
To find R2;
Mathematically, the total equivalent resistance of resistors connected in parallel is given by the formula;

Substituting into the formula, we have;

Cross-multiplying, we have;
75 * (100 + R2) = 100R2
7500 + 75R2 = 100R2
7500 = 100R2 - 75R2
7500 = 25R2
R2 = 7500/25
R2 = 300 Ohms
Answer: f=150cm in water and f=60cm in air.
Explanation: Focal length is a measurement of how strong light is converged or diverged by a system. To find the variable, it can be used the formula:
= (nglass - ni)(
-
).
nglass is the index of refraction of the glass;
ni is the index of refraction of the medium you want, water in this case;
R1 is the curvature through which light enters the lens;
R2 is the curvature of the surface which it exits the lens;
Substituting and calculating for water (nwater = 1.3):
= (1.5 - 1.3)(
-
)
= 0.2(
)
f =
= 150
For air (nair = 1):
= (1.5 - 1)(
-
)
f =
= 60
In water, the focal length of the lens is f = 150cm.
In air, f = 60cm.
<span>A. Copper is a good conductor of electricity because its atoms have a loosely held electron in their outer shell that is able to move freely to other atoms.</span>
One is for far distance the other is for close range