帮我用中文解答3个题目，---**Question 1:**
**Question Stem:**
关于原子核衰变，下列说法正确的是（□□）。
**Options:**
A. 原子核衰变后生成新核并释放能量，新核总质量等于原核质量。
B. 大量某放射性元素的原子核有半数发生衰变所需时间，为该元素的半衰期。
C. 放射性元素的半衰期随环境温度升高而变长。
D. 采用化学方法可以有效改变放射性元素的半衰期。
**Question 2:**
**Question Stem:**
如图，物块以某一初速度滑上足够长的固定光滑斜面，物块的水平位移、竖直位移、水平速度、竖直速度分别用 $x$、 $y$、$v_x$、$v_y$ 表示。物块向上运动过程中，下列图像可能正确的是（□□）。
**Chart/Diagram Description:**
Type: Diagram showing a block on an inclined plane and four velocity-displacement graphs.
Main Elements:
- A block on a smooth inclined plane, with an arrow indicating upward motion along the plane. The plane is elevated from a horizontal surface.
- Four separate plots are shown below the diagram:
- Plot A: A 2D Cartesian coordinate system with the x-axis labeled $x$ and the y-axis labeled $v_x$. The origin is labeled O. A straight line slopes downwards from the $v_x$ axis towards the $x$ axis, intersecting both axes.
- Plot B: A 2D Cartesian coordinate system with the x-axis labeled $x$ and the y-axis labeled $v_x$. The origin is labeled O. A straight line slopes upwards from the origin.
- Plot C: A 2D Cartesian coordinate system with the x-axis labeled $y$ and the y-axis labeled $v_y$. The origin is labeled O. A curved line slopes downwards from the $v_y$ axis towards the $y$ axis, appearing to be part of a circle or ellipse.
- Plot D: A 2D Cartesian coordinate system with the x-axis labeled $y$ and the y-axis labeled $v_y$. The origin is labeled O. A straight line slopes downwards from the $v_y$ axis towards the $y$ axis, intersecting both axes.
**Options:**
A. (Refers to Plot A)
B. (Refers to Plot B)
C. (Refers to Plot C)
D. (Refers to Plot D)
**Question 3:**
**Question Stem:**
如图，ABC为半圆柱体透明介质的横截面，AC为直径，B为ABC的中点。真空中一束单色光从AC边射入介质，入射点为A点，折射光直接由B点出射。不考虑光的多次反射，下列说法正确的是（□□）。
**Chart/Diagram Description:**
Type: Diagram showing a ray of light passing through a semicircular medium cross-section.
Main Elements:
- A semicircle labeled ABC, representing the cross-section of a transparent medium.
- AC is the diameter of the semicircle, forming the flat boundary between the vacuum and the medium.
- B is labeled on the curved arc ABC.
- The region above the diameter AC is labeled "真空" (Vacuum).
- The region below the diameter AC is labeled "介质" (Medium).
- A ray of light enters from the vacuum, incident on point A on the diameter AC.
- A dashed line is drawn perpendicular to AC at point A, representing the normal.
- The incident ray makes an angle $\theta$ with the normal at A. An arrow indicates the direction of the incident ray.
- The light ray is refracted at A and travels through the medium directly to point B on the curved surface.
- The light exits the medium at point B.
**Options:**
A. 入射角 $\theta$ 小于 45°.
B. 该介质折射率大于 $\sqrt{2}$.
C. 增大入射角，该单色光在 BC 上可能发生全反射。
D. 减小入射角，该单色光在 AB 上可能发生全反射。