Fenomeno de resonancia.
Espero que estoy te ayude :)
1) D
2) D.) Greater than 
Explanation:
1)
The phenomenon of total internal reflection occurs when a ray of light hitting the interface between two mediums is totally reflected back into the original medium, therefore no refraction into the second medium occurs.
This phenomenon occurs only if two conditions are satisfied:
- The index of refraction of the first medium is larger than the index of refraction of the 2nd medium
- The angle of incidence is greater than a certain angle called critical angle
In picture 1, we have 4 different diagrams. In the diagrams:
- The red arrow represents the incident ray
- The green arrow represents the refracted ray
- The blue arrow represents the reflected ray
Total internal reflection occurs when there is no refraction, therefore when there is no green arrow: this occurs only in figure D, so this is the correct option. (in figure C, there is a refracted ray but it is parallel to the interface: this condition occurs when the angle of incidence is exactly equal to the critical angle, however in this problem, the angle of incidence is greater than the critical angle, so the correct option is D)
2)
As we stated in problem 1), total internal reflection occurs when the angle of incidence is equal or greater than the critical angle. Therefore in this case, the angle of incidence must be
D.) Greater than 
1. Answer: A skydiver whose air resistance is equal to that of her weight.
A skydiver free falls under gravity but her rate of fall slows down due to drag -air resistance. when this air resistance becomes equal to her weight, the two get balanced and the body does not accelerate or decelerates.
2. Answer: Gravity
Contact forces are those which act when there is physical contact between two bodies. For example: normal force, tension and spring force.
Non-contact forces act between two bodies even when they are at a distance apart. For example: gravity, electric force, magnetic force etc.
3. Answer: The tendency of an object's motion to remain the same.
Inertia is a property of matter by virtue of which it tends to remain in its state of motion or rest. It does depend on mass of the object, more the mass, more is inertia. For example, cycle can be easily moved but we need real push hard for a car to move.
4. Answer: 254 N
The man pushes the box with 310 N force at an angle of 55 degrees to the horizontal.
we can write this in terms of horizontal (
)and vertical component (
).
Horizontal component: 
Vertical component: 
The vertical component would act towards the floor making the job more difficult to move the job.
These are adenine and guanine.
Purines adenine and guanine are double ringed structures that make up DNA. Purines have a characteristic double-ring structure composed of carbon, nitrogen and hydrogen atoms.
Each of purine's rings contain two nitrogen atoms making up a total of four within the double ringed structure. The remaining five positions within the rings are occupied by carbon atoms. The purine ring is encircled by hydrogen atoms which can be replaced by other atoms or groups of atoms to form different purines.