Why is the character always jumping to different heights in a platformer?

Question

Unity

if (hit.collider != null)
        {
            Debug.Log(hit.collider.gameObject.name);
            if (isGrounded() && hit.collider.gameObject.name != "Player")
            {
                rigidbody2D.AddForce(Vector2.up * jumpForce, ForceMode2D.Impulse);
            }
        }

Can jump high or low
jumpForce does not change
IsGrounded() code

private bool isGrounded()
    {
        float extraHeight = 0.1f;
        RaycastHit2D raycastHitGround = Physics2D.Raycast(boxCollider2D.bounds.center, Vector2.down, boxCollider2D.bounds.extents.y + extraHeight);
        Color rayColor;
        if (raycastHitGround.collider != null)
        {
            rayColor = Color.green;
        }
        else
        {
            rayColor = Color.red;
        }
        Debug.DrawRay(boxCollider2D.bounds.center, Vector2.down * (boxCollider2D.bounds.extents.y + extraHeight));
        return raycastHitGround.collider != null;
    }

Answer 1

So you apply force several times.