Explanation:

Introduction:
When light falls on an object, it either gets absorbed, transmitted, or reflected. Shadows are formed when light is blocked by an object, preventing it from reaching a surface. In this case, we need to determine which object will not block light and hence will not form a shadow.

Analysis:
Let's analyze each option to identify which object will not form a shadow:

- Book: A book is an opaque object, meaning it does not allow light to pass through. Therefore, when light falls on a book, it will block the light, creating a shadow.

- Glass: Glass is a transparent object, which means it allows light to pass through it. However, when light passes through glass, it may get refracted or bent. This refraction can create a shadow on a surface behind the glass. Consequently, glass can form a shadow.

- Cricket bat: A cricket bat is also an opaque object. When light falls on a cricket bat, it will block the light, resulting in the formation of a shadow.

- Tree: A tree is a solid object with various parts, including leaves, branches, and trunk. When light falls on a tree, the parts of the tree will block the light and create shadows on the ground or nearby surfaces. Therefore, a tree can form a shadow.

Conclusion:
Among the given options, the object that will not form a shadow is glass. Glass is a transparent object that allows light to pass through it without significant blockage. While it may cause refraction, it does not create a solid shadow like opaque objects such as a book, cricket bat, or tree.