Answer:
Solution given:
No of waves[N] =20crests & 20 troughs
=20waves
Time[T]=4seconds
distance[d]=3cm=0.03m
Now
<u>Wave</u><u> </u><u>length</u><u>=</u>3cm=3 × 
<u>Frequency</u>=
=
=5Hertz
and
Wave speed:wave length×frequency=3 ×
×5=1.5 ×
.
Complete Question
The complete question is shown on the first uploaded image
Answer:
a

b

Explanation:
From the question we are told that
The image distance is 
The value of the image is negative because it is on the same side with the corrective glasses
The object distance is 
The reason object distance is because the object father than it being picture by the eye
General focal length is mathematically represented as

substituting values

=> 
Generally the power of the corrective lens is mathematically represented as

substituting values


More attracted to the nucleus because they are further from the nucleus. In addition, the screening effect, repulsion of inner electrons on the valence electrons, will effectively reduce the attraction of the valence electrons toward the nucleus.
Resistors and reactors, for use over 600 volts, shall not be installed in close enough proximity to combustible materials to constitute a fire hazard and shall have a clearance of not less than<u> 300 mm </u>from combustible materials.
Explanation:
- The hazards associated with high power industrial resistors are primarily due to their open construction, which is necessary for cooling.
- The exposed conductors which make up the resistors can be not only a shock hazard but also a thermal burn hazard.
- When a resistor fails, it either goes open or the resistance increases. When the resistance increases, it can burn the board, or burn itself up.
- Avoid touching non-flammable resistors in operation; the surface temperature ranges from approximately 350 °C to 400°C when utilized at the full rated value. Maintaining a surface temperature of 200°C or less will extend resistors service life.
- Do not apply power to a circuit while measuring resistance. When you are finished using an ohmmeter, switch it to the OFF position if one is provided and remove the leads from the meter.
- Always adjust the ohmmeter for 0 (or in shunt ohmmeter) after you change ranges before making the resistance measurement.