What does the light screen of junior high school physics mean?

What does the light screen of junior high school physics mean?

The so-called light screen is a screen that can receive light
The function of light screen is a tool to receive light and reflect the received light back. Generally, the light screen is white and can't mirror reflection. In special cases, special colors may be selected!

What do F and f stand for in junior high school physics

F look at specific problems and then analyze them in detail
Which is f in the general title or in the picture
F can express many forces, such as pull, traction and elasticity
F is generally the friction force

There are two solid balls a and B. the density of ball a is three eighths of that of ball B, and the volume of ball B is twice that of ball A. then the mass of ball a is twice that of ball B
A 16 / 3 B 3 / 16 C 6 / 8 d 8 / 6

According to the density formula, ρ = m / V; m = ρ v,
The results show that: ρ A / ρ B = 3 / 8; V A / v b = 1 / 2;
M a / M B = p a V A / P B v b = (P A / P B) × (P A / P B) = (3 / 8) × (1 / 2) = 1 / 16;
B correct

For two solid balls made of the same material, the mass of a ball is 20g, and the mass of B ball is 0.1kg, then the density ratio of the two balls is ρ A: ρ B=______ Volume ratio VA: VB=______ ．

(1) ∵ the density has nothing to do with the mass and volume of the object, ∵ the density ratio of two solid spheres made of the same material is 1:1; (2) ∵ ρ = MV, ∵ v = m ρ, ∵ the volume ratio of two spheres: vavb = ma ρ AMB ρ B = ma ρ a × ρ AMB = Mamb = 20g100g = 15

If the volume ratio of solid metal balls made of the same material is 3:2, what is their mass ratio and density ratio

From the same material, the density is equal, M = PV = 3:2, that is, the density ratio is 1:1, and the mass ratio is 3:2

If the volume ratio of a and B hollow spheres made of the same material is 3:2 and the mass ratio is 3:1, the material density ratio of the two spheres is ()
A2:1 B 1:1 C9:2

p=m/v
p1:p2=(m1:m2)/(v1:v2)=(3:2)/(3:1)=9:2
So the material density ratio of the two spheres is 9:2
Choose C

Which one has the highest density of hollow or solid spheres of the same material
The original title is as follows:
Divide a kilogram of copper into two equal pieces to make solid and hollow spheres respectively
A. The density of solid is higher than that of hollow
B. Hollow is more dense than solid
C. It's the same size
D. The average density of the two balls is the same

The solid is big. With the same mass, the volume of the hollow is certainly larger than that of the solid. According to the density = mass / volume, we know that the density of the solid is big. And you have the wrong number for item a

The process of photosynthesis, the material connection between light reaction and dark reaction

Light reaction provides [H} and ATP for dark reaction, and then these substances are used to carry out a series of reactions in dark reaction

Reaction equations and comparison of light reaction stage and dark reaction stage in photosynthesis

Light reaction:
light
2H2O----->4[H]+O2；
enzyme
ADP + PI + light energy ----- > ATP
Dark reaction
enzyme
CO2+C5----->2C3；
ATP---->ADP+Pi
[H]+C3------------------------>C6H12O6+H2O；
ATP --- > stabilizes chemical energy
Light reaction takes place in thylakoid, which needs light, pigment and enzyme. This process produces oxygen and ATP by photolysis of water
The dark reaction takes place in the chloroplast matrix and does not need light. In this process, CO2 is fixed to C3, which is further decomposed into C5 and recycled. The reaction produces c6h1206 and H2O, and ATP is converted into stable chemical energy

The reaction equation of light reaction stage and dark reaction stage of photosynthesis
In order to have balance, sugar [(CH2O)] should be changed into glucose (C6H12O6)

12H2O+6CO2→C6H12O6+6O2+6H2O