Answer:In geometric optics, the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal. The ray can be formed by any wave: optical, acoustic, microwave, X-ray and so on. In the figure below, the line representing a ray makes an angle θ with the normal. The angle of incidence at which light is first totally internally reflected is known as the critical angle. The angle of reflection and angle of refraction are other angles related to beams.
Explanation:tik tok: Uh.amy07
<u>Answer:</u> The remaining sample of X is 6.9 grams.
<u>Explanation:</u>
All the radioactive reactions follow first order kinetics.
The equation used to calculate rate constant from given half life for first order kinetics:
We are given:
Putting values in above equation, we get:
The equation used to calculate time period follows:
where,
= initial mass of sample X = 78 g
N = remaining mass of sample X = ? g
t = time = 16.5 min
k = rate constant = 
Putting values in above equation, we get:
Hence, the remaining amount of sample X is 6.9 g
<u> Answers</u>
1. precision
2. density
3. control
4. matter
5. accuracy
6. gradation
<u>Explanation</u>
1. An indication of how close a measurement is to the correct result is called precision.
2. The mass of a substance per unit volume is called density of a substance.
3. A quantity in an experiment that remains unchanged or constant is called a control group.
4. Anything that has mass and occupies space is called matter.
5. The degree to which a measurement can be replicated is called accuracy.
6. Scale markings that denote equal units of measure is called gradation.
Wow! Very simple. Use the equation for momentum which is p=mv. You know your momentum and velocity, so do 120=m(4), now solve for m, which is 30. The mass of the child is 30 kg
Answer:
The question is not complete. see the complete question in the explanation section. The correct option is highlighted in bold
Explanation:
(a)A resistor and a capacitor are connected in series across an ideal battery having a constant voltage across its terminals. At the moment contact is made with the battery, the voltage across the resistor is
I. greater than the battery's terminal voltage.
II. equal to the battery's terminal voltage.
III. less than the battery's terminal voltage, but greater than zero.
IV. zero.
<em>Option (i) is not correct as the voltage across the resistor cannot be greater than the terminal voltage since the current is yet to flow through the resistor. Option (ii) is correct as both the resistor voltage and the terminal voltage will just equal at the instance of connection. Option (ii) can only be possible after the current must have passed through the resistor for a while not immediately after contact. Option (iv) is not correct, as this can only be possible is the contact is open.
</em>
(b)A resistor and a capacitor are connected in series across an ideal battery having a constant voltage across its terminals. At the moment contact is made with the battery the voltage across the capacitor is
I. greater than the battery's terminal voltage.
II. equal to the battery's terminal voltage.
III. less than the battery's terminal voltage, but greater than zero.
IV. zero.
<em>Option (i) is not correct as the capacitor is yet to charge talk less of the its voltage exceeding that of the battery. Option (ii) can only be correct if the capacitor is fully charged not when it has just been connected. Option (iii) can only occur if the capacitor is discharging. Option (iv) is the correct answer as the capacitor is about to start charging
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