Answer:
b. 5 N
Explanation:
Each book weighs 5 N. Therefore, five books weigh 25 N. The friction force is:
Ff = Fn μ
Ff = (25 N) (0.2)
Ff = 5 N
Answer:
Most exceptions to the trend of decreasing radius moving to the right within a period occur in the d-block.
Explanation:
- In a period as we advance from left to right, the number of valence electrons in the same shell increases due to which the effective nuclear charge increases and thus the atomic size decreases.
- In d-block atomic radius initially decreases then remains constant and increases towards the end.
- As one moves from Sc (scandium) to Zn (zinc), the effective nuclear charge increases by a factor of 1, this is because:
- The number of electrons are low in the inner shell.
- The shielding power of d-orbital is low.
- Inter electronic repulsions will be operating at a value less than the nuclear charge, which will result in decrease in atomic radii.
- As the number of electrons in the inner orbital increases the outer electrons repel one another which enables them to push away.
- Although d-orbital has less shielding power, the number of electrons present in it are high. Hence, the electron-electron repulsive force becomes dominant, this results in an increase in the atomic radii.
Therefore, most exceptions to the trend of decreasing radius moving to the right within a period occur in the d-block.
Learn more about the periodic table here:
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Answer:
41°
Explanation:
refractive index of glass, n = 1.52
For total internal reflection, the angle of refraction in rarer medium is 90°.
r = 90°
Let the angle of refraction in denser medium, that means in glass is i.
By use of Snell's law
refractive index of rarer medium with respect to denser medium, that means refractive index of air with respect to glass = 1 / n
And
i = 41°
Thus, the angle of incidence should be 41°.
