Physical Light Phenomena Review Case, a question about physical light phenomena

C Yes, the reflection in water is the imaging of the plane mirror, the principle of the plane mirror imaging is the reflection of light a, and the principle of the formation of shadows is that the light travels along a straight line.

B, the light emitted by the lighthouse is the light emitted by the light source, which is the incident ray D, and the light spot on the ground is a small hole imaging, and the principle is that the light travels along a straight line.

c, a linearity, blocked.

b I can't tell clearly, there is refraction and reflection.

dDiffraction another question d

aDiffraction or direct irradiation.

bThe straight line is blocked.

cRefraction of transparent objects.

The answer is c Reflection is formed by reflection.

A term shadow is the propagation of light in a straight line.

Item B is also a straight line propagation.

Item D is for small hole imaging.

Previous question: Because the surface of the sea and the surface of the water are like a mirror! The lights from the lighthouse and the reflection of the trees in the water are all virtual images formed by reflection! It's all a straight line of light!

Next question: D, the reason is the same as above! A: I don't know! B: Straight line propagation of light! c: Refraction of light.

Ca is the linear propagation of light, B is the linear propagation of light, C is the reflection of light, the water surface is like a mirror, and D is the imaging of small holes, which is the linear propagation of light.

I should choose C.

A and B should be considered as light propagating in a straight line, but D is not so clear, and the dense foliage is diffraction.

The ultraviolet index refers to the degree of possible damage to the human body caused by ultraviolet radiation in the sun's rays reaching the earth's surface when the sun is at its highest in the sky (generally around noon, that is, from 10 a.m. to 3 p.m.). The UV index varies from 0 to 15, and in general, the UV index is 0 at night and 15 in tropical, highland, and sunny days. When the ultraviolet index is higher, it means that the degree of erythema damage caused by ultraviolet radiation to the human body is more aggravated, and similarly, the higher the ultraviolet index, the greater the damage to ** in a shorter time.

SPF is the English abbreviation of Sun Protection Factor, which indicates the level of sunscreen effectiveness that sunscreen products can play. It is determined based on the lowest erythema dose. (You can let ** suffer less damage and avoid ** disease and other diseases).

The intensity of ultraviolet rays is predicted according to meteorological conditions, and there are 5 levels, with higher levels indicating stronger ultraviolet rays. The protective capacity of sunscreen is expressed in terms of sun protection index (SPF), and the higher the SPF value, the better the protection.

Basically, the SPF value is the time to delay sunburn, for example, if you are exposed to the sun for five minutes, you can delay it to about 75 minutes with SPF15 sunscreen. The higher the UV index, the greater the SPF protection is required to have the same effect.

Ultraviolet rays will not only tan, but also cause sunburn and cancer, so it is important to know the UV index and choose appropriate sunscreen.